Category Archives: ecology

Interview with Digital FilmMaker Magazine

I was recently interviewed for one of my favourite magazines – Digital FilmMaker! Here is the original with some of my photos from my ‘A Lion’s Tale’ shoot in Kenya; exactly a year ago. Hope you enjoy it and feel inspired to do your own!


  1. Why will this project be of interest to readers of Digital FilmMaker?

Hopefully this will be of interest to anyone wanting to shoot their first short film and have only just begun to delve into this creative, thrilling world of visual storytelling. Also, that it is indeed possible to do on a very small budget, whilst travelling to amazing places in the process! Natural history differs to drama in that you cannot predict what the wildlife ‘characters’ will do; or control a great deal of external environmental factors. However, with careful planning and preparation during the pre-production stage; it is possible to make an emotive and personal human-wildlife story that resonates with your target audience.

  1. What had you done project wise in the lead up to this?

This was one of the first and biggest project that I was completely involved in. I studied Zoology during my undergraduate years and played around with cameras in different university societies; but nothing on this scale. I lived in southern Spain all my life before moving to the UK to study as an 18-year old, and upon graduating I then came to Bristol to pursue an MA in Wildlife Filmmaking at the University of West England. I’ve known for a long time that I wanted to get into filmmaking (since I was 12), growing up watching David Attenborough and living in the countryside greatly inspired me. However, there was no academic support in Spain for me to progress in this field, and so dreamed of getting into camerawork and research at the BBC Natural History Unit in Bristol; where a staggering 40% of the world’s wildlife documentaries are made. The Master’s course certainly helped me achieve this, and part of the MA involved making our own film, drawing upon all the skills we learned alongside it. Whilst my academic background was scientific, I had always loved being creative as a child; storyboarding, drawing and writing took me to the far-flung exotic and biodiverse places I saw on our television.

Screen Shot 2017-04-27 at 21.58.46Where I grew up in Southern Spain – the light and birdlife greatly inspired me.

Watching producers and cameramen/women filming behind the scenes sparked my interest; combining the best of both science and art worlds. Then when I was 13 my father bought me my first DSLR, and could finally capture the Bee-eater birds and Short-toed eagles that were always tantalizingly out of reach. Armed with my telephoto lens, I wanted to share my passion with others but knew that being self-taught wouldn’t be enough to cut it in this competitive industry.



I therefore had a lot of catching up to do at University; joining the Leeds Student Radio societies, television and photography clubs so that I could begin to create a portfolio and apply for the MA. This included a conservation YouTube Channel about local biodiversity, and two radio programs that I produced; Weekly Wildlife Watch and the Travel Talk Show. Whilst radio and LSTV taught me how to write, shoot and focus on story; PhotoSoc helped me to compose and learn about the fundamental principles of photography.

LSRScreen Captures

  1. Who has done what on the film?

As part of the MA requirement, I saw the entire project throughout each of the processes – from the initial idea as a researcher, producer/director, camerawoman, sound, editor, SFX/mixer, grader and now social media manager promoting the content online. It was certainly challenging juggling the different roles, but I loved learning and trying out a variety of methods, techniques and styles from both the drama and natural history world. Learning through mistakes is certainly the best way forward in all walks of life, and by having total creative and editorial control I feel I’ve made something close to my childhood memory and dream. It certainly has been an extraordinary experience that I will remember forever.


  1. And how did that utilise your individual skills?

With my camerawork, I attempted to adapt different styles of shooting as well as techniques to create a visual story that would suite a film festival audience. Such immersive filmmaking techniques include those seen on various BBC series capture the animal’s perspective to add an emotional level to the story, leading to a more powerful, captivating documentary. I attempted to capture privileged views of the lion in its environment, and learned a great deal about how different documentaries are made by analyzing the shots in different sequences.


I shot in high speed in attempt to create a sense of drama for the first and last sequence of A Lion’s Tale, as well as with the use of extreme close ups (in particular the ranger patrol) for an immersive feel. The storyboarding of key sequences proved to be invaluable during the shoot, as it allowed me to focus on what I wanted to achieve in terms of framing, direction, action, speed.

Early morning starts – shooting high speed with the FS700 and Canon 100-400mm.

Equally, I took the camera off the tripod and onto a small inexpensive rig to allow for camera movement – and emphasizes the feeling and mood for a scene. The use of jibs, cranes and float cams are increasingly being used in natural history to create dynamic movement and a parallax between the scenes as seen in drama. The development of gimbals has now made this possible, although I had to resort to a very crude version of one in the end – my arms!


  1. So what’s the film about?

The Born Free story began with lions, and now 50 years later since the original film, A Lion’s Tale looks at the legacy that actress turn conservationist Virginia McKenna has left and the conflicts that lions and all wildlife face in Kenya. Set in the original heartland of the true father of lions, we journey to Meru National Park to see the Born Free team and Kenya wildlife service rangers on the front line of conflict and education. The world’s largest ivory burn is about to take place, as a symbol of Kenya’s determination to help all wildlife and stop the illegal trade. Will the next generation take up the challenge? Is there hope?

This film reveals how Kenya’s new generation of conservationists is looking out for all wildlife, including the elephants, which is witnessed at the world’s largest ivory burn event – a symbol of stopping all wildlife trade and helping humans and nature co-exist. Gaining access to this historical event was one of the greatest challenges and provided me with the opportunity to capture a unique moment in time. It has quickly been adopted in the media with several feature films and documentaries have highlighted the event (The Ivory Game, Hugh’s Ivory War). It was a truly unforgettable experience, which I self-shot and have now begun to edit into a separate film alongside this production. Filming beside my heroes, both in the conservation and camera world was one of the highlights of the shoot. The worlds press and filmmakers were gathered to document it, and it was truly a sobering sight to see the 150 tons of ivory go up in flames.

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  1. Who wrote it and what inspired that?

The story of A Lion’s Tale began with my passion for lions and chance meeting with leading ape conservationist Ian Redmond.

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This love of Africa and felines started during my childhood, when I was encapsulated by the true story of George and Joy Adamson. For me, the purpose of making A Lion’s Tale was to emotionally engage and raise awareness – focusing on one of the major issues not only concerning lions, but all wildlife in Kenya. The original Born Free story captured the emotions of millions during its release in 1956, a time when our relationship with the natural world and ‘wild’ animals was viewed negatively.


And so, whilst a large conservation movement was seemingly triggered with the momentum of a single film, it was the emotive driving force behind the true story about the real Adamson’s who released an orphaned lioness into the wild that led to actress Virginia McKenna to change her entire career and life plan – from actress to activist. I also felt it timely to produce with the upcoming ivory burn and Convention on the International Trade on Endangered Species meetings in Johannesburg. I didn’t want to write a set script; and by using the characters’ voices in the film I hope this has allowed audiences to connect with and care about the cause – not be lectured on it. The major theme of the film is hope – an emotion that all humans can relate to and a message that I believe everyone involved in the filmmaking and conservation industry can use as a device to inspire and drive change.

  1. And who produced it and pulled the project together?

I was the producer of the project and responsible for all the script-writing, scheduling, budgeting, interviewing, shooting, etc. which did take extensive planning. After conducting all the research, calling and making the contacts; getting out on location was thrilling but accounted for only 20% of the production! Logistically it was challenging, Meru National Park is not a well visited park like the Maasai Mara or Amboseli. I booked a direct flight from London Gatwick to Nairobi to go and film at the Born Free office based there, the ivory burn and then a small carrier plane into the heart of Meru for the lions.


Upon descending Meru, all I could see was a small office – no runway as such but more of a dirt track – then suddenly a giraffe galloping away from us in attempt to avoid a collision! However, the Born Free team and Kenya Wildlife Service were remarkable, they helped make the shoot a success – driving me to all the locations within this most beautiful and underrepresented of parks. The ivory burn was undoubtedly the hardest to get permits for; but with a lot a patience and incredible support from the Born Free’s president (CEO) as well as one of my contributors, Will Travers, I was fortunate enough to be able to film at the historic event.

IMG_8050 2will Travers during interview 43.38

  1. Did you have much in the way of money to play with?

Not at all! I calculated a rough budget of £3000, as most of my negotiations brought the prices down and the park fees to film were waivered in return for me editing a separate version for them. This may seem ludicrous to most drama filmmakers, but in wildlife the budgets are far smaller and so this is where precision also plays a part throughout the production process. In total it cost £2600 for a 10 day shoot – this of course excludes all the pre-production and post costs as I was the one researching, filming, directing/producing, editing, grading, sound mixing; however the music was beautifully composed by MA student Richard Collins as part of his course. The facilities were provided by my university and the training in advance, but also a lot of practical reading and watching hours and hours of ‘How to…’ videos! Kit was also borrowed from the university and so most of the budget was spent on flights and accommodation. I did however set up a crowdfunding campaign and managed to raise half the funds to go; kind support from family, friends and strangers alike. IndieGoGo was the platform I used as it’s less risky if you don’t hit your top target.


  1. And what were your kit choices for this film?

Kit wise I used what was available at university; the Sony FS700 with the kit lens (18-200mm f/3.5-6.3), the 50mm f/1.8, 100mm Canon f/2.0 primes and the 100-400mm with the EF metabones adaptor. The telephoto was crucial for getting close to the action when it would have otherwise been too far and dangerous. This was especially the case with the lions! For sound; radio mics, Sennheiser 416 with the 522 mixer, and a Tascam for good measure – the latter was used to record atmos in the field. The wild sounds of Kenya truly are as vivid and vibrant as you would imagine. I loved recording the young group of school children who sang to us, it stirs up many joyful memories when played back.

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The film was edited on Premiere Pro, Pro Tools, and graded in Da Vinci. In hindsight, I would have loved to have taken an DJI Ronin MX gimbal, FS7 and a Phantom 4 Pro drone for the aerials; but very grateful for the access to the kit we had, especially as students. You are only ever truly limited by your own imagination.

  1. Where does it sit alongside the rest of your portfolio of work?

In terms of technical difficulty, time scale, and aspiration to make – it’s right up there! As I am sure many of you reading this have experienced, we are our own worst critics. However, this is one project that I was excited and dare I say it, proud to have made. It’s been a life-long ambition to meet my heroine Virginia McKenna, and never thought I would get to experience the true Born Free story alongside the incredible people who keep that spirit of the Kenyan wilderness alive.

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  1. So where are you with the film right now?

The film is now complete, however there are a few colour grading tweaks being done by a professional, as I now have the confidence to hit the bigger festivals! It was something that I lacked skill-wise, and could only grade and colour correct to a certain extent. I’m looking forward to the festivals and so far, it’s collected awards at six in the US, UK, India and Spain; winning recently at the Wild Film Fest in Falmouth. But more importantly, it’s been shared in the schools back in Meru where it was filmed, and where the real difference in changing attitudes towards these amazing animals can be made. They are the generation that can make all the difference.


  1. How is it looking at this stage in the game?

All finished! It took me 10 months in total, with my fellow course mates and I recently enjoyed a screening of our films at the Everyman theatre in Bristol. It was incredibly rewarding to see in on the big screen with family and friends, as well as some BBC staff who came to support us. A project that you are so involved in does, to a certain extent, take over your life for a while – but it’s such an incredible feeling to see the end creation. Although I always say that if I didn’t set myself a cut-off point, I’d be forever editing! I received a heartfelt letter from Virginia McKenna, my main character, about how much she enjoyed the film – and that was very special indeed as she had a huge influence on me when I was growing up.

Incredibly exciting day at the #premiere of #alionstale @ the #Everymantheatre #Bristol😀😎🦁🐾🎞 #mawfonlocation

A post shared by Tania Rose Esteban (@tania_esteban23) on

  1. And how do you plan to promote it given that this is such a competitive marketplace?

I plan to promote it through a variety of social media platforms; Twitter, Instagram, Facebook, etc. and by connecting with influential Born Free supporters who can use their media presence to share and connect the film with the intended audience. Equally by continuing to enter festivals, I hope to promote it further worldwide. I also shot some 360 VR ‘behind the scenes’ clips to showcase on my website, especially during the ivory burn. Tapping into this market is key to reaching the younger audiences or those not necessarily interested in wildlife. During the run up to the film’s creation, I built up an online audience offering exclusive clips and images from the shoot as well as other stages of its development. It’s really important to engage with them and respond to what they have to say; as well as offer any advice. They also want their voice to be heard.

  1. Can you tell us about the other projects you’ve been working on?

Screen Shot 2017-02-06 at 19.05.27At the moment, I am employed at the BBC as a researcher with the digital team – one of the most innovative, creative and energetic group you’ll meet at the Natural History Unit! I’m loving every moment, most recently we released exclusive Snapchat stories for Planet Earth II in the US, and now I’m working on another digital project associated with the Blue Planet series. It’s incredibly exciting as you get to help out in various productions with different roles. Film-wise I do have a couple of personal project ideas in the pipeline, and I am very keen to shoot another short using the superb Panasonic GH5 – watch this space!

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  1. How do they differ from this one?

They differ in that they are not located in Africa! I’ve always been incredibly drawn to the continent but now have storylines I’m researching in Australia and Japan, both having more of a cultural-human element to them. However, another short I’d love to shoot is more of a pure wildlife blue-chip style, and I now have access to better equipment and financing to facilitate the projects.

  1. What is your favourite genre and why?

I’m a little biased when saying I adore making natural history, but it’s something I live and breathe every second of the day. For centuries, humans have told stories to make sense about the world- illuminating behaviour, making order out of chaos and to create moral meaning. It’s the way we can comprehend and pass on information, with which we have the insatiable need for form and structure in the way we tell them. Natural History has been documented for thousands of years through visual, physical and audible means, whether through the primitive Stone Age depictions of a hunt through cave paintings, to the now pioneering ultra-high definition wildlife films. Nature is endlessly fascinating and beautiful, and as a curious person it’s something that I’m always passionate and keen to share with others. I am certain most of us have this desire to learn about the world around us. I do of course enjoy watching a great variety of programmes and films; adventure, comedy, sports, fact ent, animation and action! You can learn many lessons from different genres.


  1. Are there other genres that you’d like to tackle?

Natural History will always be my passion – but I do believe you can cross-pollinate genres and get interesting results. A superlative example the award-winning success Virunga directed by Orlando Von Einsidel; where wildlife documentary meets investigative journalism. It combines elements of “The seven key steps of story structure” as described by screenwriter John Truby, and regardless of it being a non-fiction film, Virguna also contains strong dramatic elements and a classical story structure of good versus evil. Battles depicted through the civil war and conflict between the park rangers and the oil companies are also tied in with the need to survive, along with the desire to exploit natural resources for profit. These all conjoin into a single cause and effect pathway through the combined use of a ‘run and gun’ shooting style and profound emotive pauses. It would be interesting to try a more daring, journalist approach with a conservation story – thrilling audiences by being immersed right in center of the action.

  1. So what is the filmmaking climate like in your neck of the woods?

Wildlife filmmaking is quite different to drama in my experience. Whilst we are adopting more cinematic techniques and technology using gimbals and aerials to create a parallax and dynamic edge; the set-up times, cast (!), budgets, and approach are quite different. I worked recently on a drama set as a camera assistant and found the whole thing fascinating; there certainly are no repeat takes when filming a wild animal in action! Equally, whilst in drama you have many specialized roles such as focus pullers, gaffers, and make up; wildlife crews are noticeably smaller as costs for location shoots would soon quickly rise – budgets are noticeably smaller. Most crews are a jack of all trades, and you learn quickly how to be as multi-skilled and useful to a team as possible. It’s the most incredibly rewarding and thrilling industry, and you never quite know what animals you will see and how they will behave. If you’re lucky, you can capture unique behavior that’s never been seen before.


  1. Are you at the stage of making any money from this as yet?

No, I decided that this project would not be for profit, despite my access to the ivory burn. I wanted this to be an educational and inspirational piece and shared far and wide; available to anyone with an interest in wildlife and Africa. Now that I know I can make a short film – next time may be different!

  1. So where do you see this filmmaking route taking you in the future?

I hope to follow in the footsteps of some of my filmmaking heroes; Sophie Darlington, Sue Gibson, Justine Evans – the best female camerawomen in our industry! But equally, I do want to pursue my passion for producing and continue to create compelling stories. I recently met the producers who worked on Planet Earth II who were incredibly inspiring- their work is truly in a league of its own. David Attenborough of course has been the greatest source of inspiration; and If I can make entertaining, emotive and compelling films that inspire others to want to make even the smallest of positive differences on our beautiful planet, then I’ll be a very happy earthling indeed.


Urban Bat Ecology

 Urban Growth

The rapid global urban population growth seen in the last 65 years, from 746 million to 3.9 billion in 2014, has had significant impacts on bat species richness and abundance (WUP 2014, Kunz et al 2007), due to habitat loss, fragmentation, degradation (Altringham, 2011), chemical pollution, barrier effects, introduction and facilitation of invasive species and a decline in prey species (Wickramasinghe et al, 2004, Lentini et al, 2012, Berthinussen & Altringham, 2012). Many studies are currently looking into the possibility of using bats as bioindicators of environmental change (Wordley et al, 2014, Russo et al, 2014), due to Chiroptera being the world’s second most speciose mammalian order (second to Rodentia), numbering 1232 species (Kunz et al, 2011).

urban bats 3 bats urban 1

Equally, their widespread distribution and sensitivity to even minute perturbations means they could reflect the status or possible risk of such change in other species (Jones et al, 2009). Some of the responses to change can be seen with declines in abundances, population size, range distributions and behaviour (Altringham, 2011). Thus, it is important to determine the relative abundance of bats in urban areas compared to rural and suburban, and see whether an association with particular urban features are limiting or enhancing their ability to forage and roost there. This information has vital applications for conservation, as 82% of the UK is urbanised and is steadily increasing (United Nations World Urbanization Prospects, 2015). Thus, policy makers with knowledge regarding the ability of certain bat species to adapt (synurbic), or not (more vulnerable and sensitive species) to one of the greatest land use changes seen in the last century, can act to reduce the impact by lobbying with businesses, developers and politicians (Altringham, 2011, Russo, et al, 2014).

urban bats 2

Importance and impacts of an urban landscape on bats- Urban foraging and roosting

Bats form some of the largest seen mammalian assemblages, (Jones et al, 2009), with up to 40 million in a single cave-roosting colony (Seimers et al, 2001). The potential of urban areas being suitable areas to provide bats with useable roosting and foraging habitats is becoming an ever more prevalent area of research. Thus, it is of vital importance to study how bats are using such anthropogenic landscapes (Bellamy et al, 2013). It is essential that research from a wide variety of urban landscapes is conducted in order to assess the relative importance of particular variables and landscape features, as some are more important to different species, which each exploits the landscape differently (Altringham, 2011, Coleman & Barcley, 2011). It is this specificity of each species responding to urbanization differently which is vital to conservation and management policy. Each bat has evolved is perfectly adapted to each habitat, in terms of wing morphology, diet (ecological niche), echolocation call, hibernacula and behaviour (Altringham 2011, Threfall et al 2008). Thus some exhibit behavioural plasticity and can adapt to urban environments, enabling them to effectively exploit their habitat without the disruption of roads, light pollution or buildings (Russo and Ancillotto, 2014, Stone et al, 2011). This has been seen in bats with long narrow wing morphology with a high wing loading, as open air foragers are largely unaffected by urbanization (Norbeg & Rayner, 1987).

Hunting phases of bats. Search phase involves a high frequency component (45-55kHZ) as well as CF constant frequency with longer pulses as it detects prey. Then the calls increase in frequency with additional harmonic components as the bat approaches its prey. Then terminal phase the bat can emit calls at 2ms as it hones in on it.

The ability of synanthropic bats to dominate urban foraging areas can be problematic for the less well adapted species (Silvis et al, 2014, Russo and Ancillotto, 2014). Some studies even suggest urbanization may result in greater competition between the synurbic and less well adapted species, as implicated by Arlettaz et al (2000). The study suggested that the decline of the Rhinolophus hipposideros in Wales may be due to the expansion of Pipistrellus pipistrellus, whose populations have increased as a result of greater feeding efficiency with artificial lights (Warren et al, 2002, Lacoeuilhe et al, 2014), normally avoided by the lesser horseshoe bat. Equally, in one study investigating the activity of insectivorous bats in Panama Canal, it was shown that only a few dominant Molossus were able to adapt to urbanized areas due to their high wing loading and aspect ratio (Jung et al, 2011). This was in contrast to a majority of clutter-specialist species recorded which foraged within the forest and the forest edge.

Advantages provided by artificial roosts in urban areas include homoeothermic benefits, in particular for pregnant females by reducing the energetic costs of maintaining their body temperature within the thermal neutral zone (Lausen & Barcley, 2006). Therefore the potential to provide bats with artificial roosts is of interest to many conservation bodies, which aim educate and encourage public concern (Altringham, 2011). Artificial bat boxes have been shown to be particularly exploited by opportunistic and synurbic P.Kuhii (Angelli et al, 2011). However, the lack of rigorous scientific testing of their effectiveness is yet to be determined in lesser adapted species (Altringham, 2011), and with thorough monitoring and further studies into ‘bat box’ preferences, a more valid account of their potential use may be of value to policy makers (Russo & Ancillotto, 2014).

Importance of Water in urban areas

Bats are vulnerable to evaporative water loss as a consequence of their morphology and large surface area to volume ratio, as well as high energetic costs with the ability to fly (Razgour et al, 2010). Within urban areas, open artificial sources such as ponds, ditches and swimming pools provide bats with fundamental opportunities to drink and forage. Certain species show preferences over these larger, less cluttered and open bodies of water (Seimers et al, 2001). The reduction in pulse-echo overlap, ability to detect spectral shift and high insect abundance over still water sources (Altringham, 2011) can attract large numbers of bats to urban and modified sites (Vindigni et al, 2009). Such examples can be seen in North Carolina, where studies looking at the importance of managed water bodies over natural wetlands revealed significantly higher bat activity by heliponds, despite equal densities of insects at both sites (Vindigni et al, 2009). Equally, studies on Greek islands showed that bats will also use artificial water sources such as swimming pools due to the lack of natural sources in such arid habitats, with minimal annual rainfall (Davy et al 2007).

If you want to find out more about how YOU can help bats, head over to the Big Bat Map and the Bat Conservation Trust!

Major threats facing keystone species and the consequences for biodiversity

cell press logo  butterfly

Tania R.E –Esteban 1

School of Biology, Faculty of Biological science, University of Leeds, UK, LS2 9JT


The global threats facing keystone species is significantly impacting levels of biodiversity, due to the disproportionate effects keystones have on entire communities. They influence trophic interactions and provide ecosystem services of vital importance to the economic, social and cultural well-being of humans. It is therefore in our interest to establish the threats, the individuals most at risk, the potential cascading effects on ecosystems and how we are to manage them successfully in terms of reintroduction or mitigation. In this essay I review the major threats to a variety of different keystone species (at all trophic levels), examine how this influences levels of biodiversity and what effects they have on entire ecosystems. I also evaluate the current and potential management strategies that facilitate networks and allow them to be more resilient to future environmental change. Our knowledge of the concepts that underpin the fundamental basis of ecology can help us confront this as one of the greatest challenges in ecology.

Concept of Keystones

In different ecosystems, each specie plays a role within a community and can influence levels of biodiversity. However, the relative impact of each species can vary in terms of importance [27]. Such species that have disproportionate effects on ecosystems are known as keystone species [39]. According to network theory, keystones are intimately linked via ecological networks of highly connected and complex webs (Box 1, [9]). These include species at different trophic levels. Apex predators exert top-down effect on these levels, known as trophic cascades; whereby these strongly connected species indirectly influence community structure and ecosystem function [37]. The robustness of food webs to species removals varies, depending on the species and ecosystem type, where certain removals have greater impacts on ecosystem functioning and structure. Many apex predators are classed as keystone species because of the secondary extinction impacts of their removal on other species [7]. Predators directly impact upon herbivore numbers as well as indirectly through risk effects [34]. This then influences the relative abundance of producers- hence a ‘cascading effect.’

trophic cascasde

Equally, predators sustain levels of biodiversity via the suppression of other competitors (mesopredators) through competitive exclusion, and allow other species to co-exist [20]. Predatory release occurs when the apex predator is removed, increasing populations of the less competitive mesopredator. This then leads to a decline in its prey. Predator-prey dynamics as well as competition between intra and interspecific species also influence the structure of the food webs [1, 27]. The length of food webs can also greatly influence the direction of the cascade according to the exploitation ecosystem hypothesis [11]. These natural processes can be perturbed by threats to apex predators- whereby the removal of such keystone species leads to the concept of trophic downgrading [10]. As well as this, there is an alternate stable; where ecosystems are disturbed to such an extent that the cascade shifts from its prior state to another- when a tipping point is reached [10].

Box 1- Network theory

The fragile nature of ecosystems has been explored by Sole and Montoya [36], on the basis that if the nodes that connect individuals are randomly removed in a network, it remains stable. However, when highly connected individual are removed, this results in cascading effects and interference throughout the rest of the network. These keystone individuals form the framework and structure of the network. In real ecological networks, strong evidence for the removal of predators are known to not only directly impact its prey, but also have indirect effects via top-down forcing. Ecosystems processes such as primary production, nitrogen cycling and the establishment of invasive species are also affected (Figure 3 [10]).

network theory


Keystones – threats to a complex web of interactions

Habitat destruction

There have been major declines in biodiversity within recent decades, in what has been described as the 6th mass extinction event [27]. The threats facing keystones and the ecosystem services they provide are predominantly anthropogenic [19], and habitat loss is arguably one of the greatest [15]. For example, the Yellow and Black-Casqued Hornbills are both in decline, which has been correlated with deforestation in Nigeria as well as forest sections along the Ivory Coast [28]. This is problematic in that the genera Ceratogyma are key seed dispersers of fruiting trees, and play an important role in maintaining the heterogeneity of forests and species diversity via gene flow [28]. Because of the large spatial distribution of their territories [45], up to 22% of lowland tropical rainforest species are dispersed by the 3 hornbill species within this genera [23]. Cultural ecosystem services include traditional ceremony wear as well as other benefits to the keystone tree species, Ficus, which in turn provides economic services to local tribes’ people. It is also an important food source for other species within the ecosystem [23].



Other threats to keystones include the urbanization of many habitats. Increased contact between humans and species drive them to exhibit behavioural plasticity and alter their behaviour [33]. A majority of studies indicate that increases in urban environments decreases species richness [35], due to disturbances in breeding patterns, anti-predator behaviour, fitness, selection of habitat and overall population size. This has cascading effects along trophic levels [2]. The black-tailed prairie dog, a keystone specie, contributes to the health of steppe habitats by mixing the soil. This increases plant productivity and landscape heterogeneity as well as providing coyotes with a food source [3]. Their overall numbers have decreased as a result of increased urbanization. However, in contrary to the risk-disturbance hypothesis, where increases in anti-predatory behaviours (such as vigilance) are seen, some populations exhibiting behavioural plasticity have reduced their vigilance due to habituation [12]. This has negatively impacted the vegetation due to increased foraging time, which has ‘rebounding’ effects back up the trophic cascade, on other herbivores and predators [33].

Climate change

Complex plant-pollinator webs are also disturbed by habitat destruction due to their sensitivity to perturbation [29]. This is the case with the keystone plant mutualist, Heliconia tortuosa,

Figure 1. The warming trend set to continue: (Left) Projected increases in temperature by 2081-2100 if mitigation and use of renewable resources is adopted. (Right) These are the predictions if the business as usual strategy continues (source: IPCC, Fifth assessment, 2014).


which supports a variety of hummingbird species, and is considered a central node in this web interaction [17]. Recent work has provided evidence for the fragmentation hypothesis, where forest composition is fundamental to the reproduction of H. tortuosa. Thus, the reduction in heterogeneous landscapes due to deforestation is thought to alter both plant distribution and pollinator behaviour, leading to declines in both populations [29]. Equally, other systems have also shown that deforestation alters pollinator behaviour. Phaethornis hummingbirds will take longer flight paths to avoid deforest patches and agricultural landscapes, decreasing pollinator efficiency. This affects the survival of plant species dependent on this mutually beneficial ecological interaction- and has led to regional declines in biodiversity [16].


Climate change also poses a major threat to the biodiversity of keystone pollinators (such as bats, bees and birds [19]). One third of the world’s crop production is met by the ecosystem services provided by insect pollinators [30], with agricultural pollinator services estimate to be worth £120 billion per acre, annually [40]. Phenological shifts are also increasingly being observed, with the impact evident in both pollinator and plant keystone species [4]. In Japan, seed production in Corydalis ambigua and Gagea lutea decreased due to the warmer temperatures causing them to bloom earlier, resulting in phenological mismatching with its key pollinator, Apis Mellifera. Consequently, this reduced pollination efficiency and success [31]. Climate change has also altered bee distributions and caused phenological shifts in their flight period. Predictions suggest that the spatial shifts in bee movements will be faster than that of its food resource, also causing phenological mismatching and decrease wildflower pollination [4]. Therefore, climate change poses not only a threat to the keystone plant-pollinators, but to other communities dependent on wildflower meadow species [31]. This highlights the fragility of these mutualistic interactions as key nodes in an ecosystem, due to their varying response to temperature change.

polar bear 1

A major issue with climate change is predicting the influence it will have on biological communities in the future [13]. The polar bear (Ursus maritimus) is an apex predator in the Arctic ecosystem which is very sensitive to changes in sea ice cover, where it hunts, migrates and reproduces [25]. The rate of temperature increase in the Arctic and northern regions have doubled in recent years, reducing sea ice cover [24]. In particular, over the past 30 years, the Western Hudson Bay has seen earlier ice break up as well as reduced snow fall (Figure 2). The impact on ringed seals (a keystone specie) with longer ice-free summers has subsequently lead to changes in polar bear behaviour [25]. The continuity of this pattern threatens seal pup survival as they are forced to swim for longer periods of time in open water, exposing them to predation [13]. Ringed seals provide polar bears with net wet weight calorific gains of 2.2-5.3 kcal/g [43], and the decreased recruitment of ringed seals has driven polar bears to target nesting birds, as they are unable to gain sufficient energy [25]. This warming trend is set to continue with possible increases in temperature of 5.0-6.4˚C by 2081-2100 (Figure 1, [24]).

Figure 2: Sea ice extent between 1979-2012 throughout the summer months. Evident loss seen annually. (Source: Iverson [25]).

Hunting and over-exploitation

Hunting and over exploitation is also a prevalent threat to many keystones worldwide. The removal of a keystone predator is a major cause of secondary extinctions, demonstrating the strong influence of top-down effects on lower trophic levels [10]. This was seen with the expatriation of the Grey wolf in Yellowstone during 1935 (due to hunting), which increased populations of elk as a result of predatory release [39]. Increased levels of browsing on aspen, cotton and willow saplings in riparian river systems led to a more homogenous landscape and reduced diversity [34]. The wolf played a vital ecosystem role by maintaining diversity as well as healthy numbers of mesopredator populations. Classic studies of the consequences of predator removal are also illustrated with sea otters [10]. Enhydra lutris was nearly hunted to extinction by Russian fur traders at the beginning of the 20th century, resulting in the predatory release of sea urchins, which reduced Kelp forests by intensively over-browsing [42]. However, with the return of the otter during the 1970’s to certain areas, the recovery of the kelp forests was observed due to the effects of top-down control on urchins. The kelp populations in regions where otters were unable to recolonize did not recover [11], demonstrating how the impact of hunting can alter and result in the simplification of food webs.


The general pattern of global declines in apex predators is a cause for concern, due their strong connectedness in ecosystems and influence in altering the stability of food webs [19]. This is less well studied in marine ecosystems [20]. For example, sharks are apex predators in marine ecosystems [22], and are threatened by hunting. Demand for shark fin during the 90’s increased mortality rates by 80%. Many debate the function of sharks as keystone predators [8], however more recent studies suggest that although not all shark species can be described as keystones, some are key in structuring some ecosystems [44]. Indeed, strong arguments made by Estes et al., [10] concluded that the top-down effects exerted by apex predators are equally as influential as bottom-up effects. In Western Australia, Tiger sharks are considered a keystone apex predator; as mesopredator diversity (dolphins) and herbivores (dugongs) abundance are indirectly affected by the “seascape of risk,” as well as by direct predation [20]. 15 years of data collection in Shark Bay has supported the idea that the non-predatory effects of top apex consumers (predator keystones), play a pivotal role in influencing ecosystems [10]. Thus shark declines are affecting mesopredator numbers and behaviour, with unknown consequences on the rest of the aquatic communities [44].

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Clearly, hunting apex predators can have detrimental, aggregating effects on lower trophic levels, both directly (via predation) or indirectly (through the landscape/seascape of fear concept). Equally, the idea that keystone’s play a role within and across communities [27], was seen with the decline of sea otters in the Aleutian archipelago populations due to increased predation by Orca [42]. The overexploitation of fish stocks in these waters in turn reduced populations of pinniped that fed on them [11]. This altered the orcas behaviour which began targeting otters as an alternative food source. Kelp forests once again declined as urchins were free of predation. This is known as the exploitation ecosystems hypothesis, where the food-chain length determines the level of influence and control top-down or bottom-up systems have in the primary productivity of ecosystems [10, 11].

Great White Shark

Future: Management, mitigation and reintroduction


In terms of keystone species, the challenges of managing and mitigating their decline arise due to the complexity and interconnectedness between the many species they affect within ecological communities [5]. For example, managing the declines of seed dispersers is hard due to the large spatial ranges of their territories and difficulty in quantifying dispersal rates [23]. The extent to which urban-adapted keystones will affect the rest of the community depends on their ability exhibit behavioural plasticity and adapt, which varies between species and landscape scale [35].

The threat of climate change is also difficult to predict, thus is hard to prevent plant-pollinator loss in the future as phenological shifts continue at different rates [4]. Similarly, the uncertainty surrounding model projections of sea ice loss threatens the future survival of many Arctic species [25]. In aquatic systems, the lack of protection out of marine conservation areas and the extensive movements of keystone predators such as sharks, creates problems in managing and mitigating their decline [21, 22].

Equally, the overall concept of what constitutes a keystone species provides difficulties in management [7]. The definition can be broadly used to describe a spectrum of keystone types, which is confusing and problematic for conservation policy [7]. With an increasing number of species being given ‘keystone status,’ the lack of consistency in defining them more scientifically is rapidly becoming a challenge in itself [27].


Identification of which trophic direction is most influential in affecting levels of biodiversity within communities is controversial [10]. Often, it is dependent upon the ecosystem as well as the keystone specie. Some argue that primary production controls ecosystems bottom-up [18]. Others believe predatory top-down control is more influential, and is currently gaining more support due to the mounting evidence that global predator declines have significant impacts on communities and ecosystem processes (Figure 3, [10]). However, even if top-down systems were recognisably more important in structuring ecosystems, it is hard to determine the most prevalent impact predators have in influencing interactions within food webs- directly (through predation/lethal) or indirectly (risk effects/non-lethal [34]).

Figure 3: Indirect impacts of apex predators on different ecosystem function and processes (Source: Estes et al [10]).

Indeed, this is the case with sharks, where the importance of risk effects might be underestimated [26]. In terrestrial ecosystems, the ‘landscape of fear’ as well as direct predation by wolves is being taken into account in studies of natural systems, (eg: Białowieża Forest, Poland) in order to consider the nonlethal effects on herbivores [32]. Proposals by Manning et al., [34] suggest that controlled experiments in the Scottish highlands would provide much needed data and viable evidence for their reintroduction. However, public opinion is often divided in terms of reintroductions [37], and the funding and costs of trial experimentation are deemed wasteful [32].

The nature of predicting ecosystem response with the removal of a keystone is also very difficult when taken from a stable environment- where prior knowledge of the response in unknown [36]. Only a few studies have examples of networks that are partially mapped [5], and the substantial lack of data on a range of ecosystems makes management difficult [36]. Much earlier research does not indicate the strength of each trophic link, thus it is difficult to compare to the current consistent and empirically accurate data. Even when disrupted, other factors such as intraspecific competition can alter the response, and may take many years for the effects to propagate in the ecosystem [10]. Current strategies by the US Endangered Species Act fail to incorporate this [41].

Possible solutions?

It is vital that scientists are able to quantitatively asses the relative contribution of each proposed keystone [36]. Only then can policy makers implement management strategies that target and focus on protecting species that have the most important functional role- rather than the rarest specie [27]. We must also therefore demonstrate their functional importance before policy-makers act on the impetus of the analogical term of a keystone [7]. Of equal importance is understanding the connectivity of networks as well as attempting to mitigate the threats facing keystone apex predators. The geographic spatial scales at which natural or previously manipulated experimental removal experiments varies enormously, thus must also be considered in future reintroductions and management plans [39].


As already established, complex ecological concepts are hard to manage as many factors feed into the function, stability and persistence of food webs; including biotic and abiotic factors [10]. It is clear how important abiotic interactions greatly influence ecosystems and community structure and function, and must be considered if we are to manage and mitigate the effects of current and future climate change [19]. Therefore, as the fifth assessment by the IPCC suggests, anthropogenic climate change policy should focus on mitigation by following resilience pathways and realising adaption measures towards a more sustainable future [24]. If we are to reduce the number of extinctions, policy must also address the source of the problem; fossil fuel consumption, to mitigate the severe effects it could have on vulnerable keystones and their habitat [24].


Other concepts such as network theory have helped explain how the systematic targeting of particular keystone individuals is far more destructive than random removal [36]. Therefore fisheries must implement this into their harvesting methods and reduce their impact on sharks by implementing annual moratoriums to prevent over harvesting. This will require international cooperation to account for the spatial movements of these keystone predators [44].


The threats facing keystone species may arguably have the greatest impact upon ecosystem function and stability globally [10]. Keystone predators in particular play an important role as their loss is a cause of many secondary extinctions [21]. The complexity of these networks cannot be undermined, and scientists must now be able to predict and further assess why certain keystone species are more robust or more at risk from collapsing early on than others. This will determine which species will have the greatest impact upon the stability and function of communities [46]. Additionally, completion of fully described networks will need to be of a multidisciplinary manner, in order to expand upon the current knowledge of these systems. Mitigating the threats as well as assessing the success of keystone reintroductions in influence levels of biodiversity is also key [44]. The reduction of harmful human activities is also necessary in order to prevent future extinctions and declines in biodiversity [24]. Ultimately, the solutions to the challenges facing keystones and ecosystem function are not simple. However, further knowledge of how these systems work and the implementation of efficacious management strategies will lead more efficient restoration and protection.

cameleon Animals



  1. Allesina, S, and Pascual, M. (2008) Network structure, predator-prey modules, and stability in large food webs. Theoretical Ecology 1, 55-64.
  1. Angeloni, L, et al. (2008) A reassessment of the interface between conservation and behaviour. Anim Behav 75, 731-737.
  1. Bangert, RK and Slobodchikoff, CN. (2000) The Gunnison’s prairie dog structures a high desert grassland landscape as a keystone engineer. Journal of Arid Environments 46, 357–369.
  1. Bartomeus, I, et al. (2011) Climate-associated phenological advances in bee pollinators and bee-pollinated plants. Proceedings of the National Academy of Sciences of the United States of America 108, 20645-20649.
  1. Berlow, EL, et al. (2009) Simple prediction of interaction strengths in complex food webs. Proceedings of the National Academy of Sciences of the United States of America 106, 187-191.
  1. Brose, U, et al. (2006) Allometric scaling enhances stability in complex food webs. Ecology Letters 9, 1228-1236.
  1. Cottee-Jones, et al. (2012) The keystone species concept: a critical appraisal. Frontiers of Biogeography 4, 117-127.
  1. Dulvy, NK, et al. (2008) You can swim but you can’t hide: the global status and conservation of oceanic pelagic sharks and rays. Aquatic Conservation-Marine and Freshwater Ecosystems 18, 459-482.
  1. Dunne, JA, et al. (2002) Food-web structure and network theory: The role of connectance and size. Proceedings of the National Academy of Sciences of the United States of America 99, 12917-12922.
  1. Estes, JA, et al. (2011) Trophic downgrading of planet earth. Science 333, 301–306.
  1. Estes, JA, et al. (1998) Killer whale predation on sea otters linking oceanic and nearshore ecosystems. Science 282, 473-476.
  1. Frid, A, and Dill, L. (2002) Human-caused disturbance stimuli as a form of predation risk. Conserv Ecol. 6, 31-54.
  1. Ferguson, SH, et al. (2005) Climate change and ringed seal (Phoca hispida) recruitment in western Hudson Bay. Marine Mammal Science 21, 121-135.
  1. Garibaldi, A. (2009) Moving from model to application: Cultural keystone species and reclamation in fort MCay, Alberta. Journal of Ethnobiology 29, 323-338.
  1. Gross, L. (2006) Predicting Species Abundance in the Face of Habitat Loss. PLoS Biol 4. (doi: 10.1371/journal.pbio.0040336)
  1. Hadley, AS, and Betts, MG. (2009) Tropical deforestation alters hummingbird movement patterns. Biology Letters, 5, 207-210.
  1. Hadley, AS, et al. (2014) Tropical forest fragmentation limits pollination of a keystone under story herb. Ecology 95, 2202-2212.
  1. Hairston, NG, et al. (1960) Community structure, population control, and competition. Am Nat 94, 421-424.
  1. Harley, CDG. (2011) Climate Change, Keystone Predation, and Biodiversity Loss. Science, 334, 1124-1127.
  1. Heithaus, MR, and Dill, LM. (2006) Does tiger shark predation risk influence foraging habitat use by bottlenose dolphins at multiple spatial scales? Oikos 114, 257–264. (doi:10.1111/J.2006.0030-1299.14443).
  1. Heithaus, MR, et al. (2008) Predicting ecological consequences of marine top predator declines. Trends in Ecology & Evolution 23, 202-210.
  1. Hinman, K. (1998) Ocean roulette: conserving swordfish, sharks and other threatened pelagic fish in longline-infested waters. Leesburg: Harvard Press.
  1. Holbrook, KM, and Smith, TB. (2000) Seed dispersal and movement patterns in two species of Ceratogymna hornbills in a West African tropical lowland forest. Oecologia 125, 249-257.
  1. IPCC, (Intergovernmental Panel on Climate Change). 2014. Summary for Policymakers in Impacts, Adaptation, and Vulnerability. Part A. United Kingdom and New York: Cambridge University Press.
  1. Iverson, SA, et al. (2014) Longer ice-free seasons increase the risk of nest depredation by polar bears for colonial breeding birds in the Canadian Arctic. Proceedings of the Royal Society B-Biological Sciences 281, 43-51.
  1. Johnson, SD, et al. (2009) Pollination and breeding systems of selected wildflowers in a southern African grassland community. South African Journal of Botany 75, 630-645.
  1. Jordán, F. (2009) Keystone species and food webs. Philosophical Transactions of the Royal Society B: Biological Sciences 364, 1733-1741, (doi:10.1098/rstb.2008.0335).
  1. Kemp, AC. (1995) The Hornbills. Oxford: Oxford University Press.
  1. Klein, AM, et al. (2007) Importance of Pollinators in Changing Landscapes for World Crops. Proceedings of the Royal Society 274, 303–313.
  1. Kremen, C, et al. (2007) Pollination and other ecosystem services produced by mobile organisms: a conceptual framework for the effects of land-use change. Ecology Letters 10, 299-314.
  1. Kudo, G, et al. (2004) Does seed production of spring ephemerals decrease when spring comes early? Ecological Research 19, 255-259.
  1. Kuijper, DPJ. et al. (2014) What Cues Do Ungulates Use to Assess Predation Risk in Dense Temperate Forests? Plos One 9, 12-16.
  1. Magle, SB. and Angeloni, L M. (2011) Effects of urbanization on the behaviour of a keystone species. Behaviour 148, 31-54.
  1. Manning, AD, et al. (2009) Restoring landscapes of fear with wolves in the Scottish Highlands. Biological Conservation 142, 2314-2321.
  1. McKinney, ML. (2008) Effects of urbanization on species richness: A review of plants and animals. Urban Ecosystems 11, 161-176.
  1. Montoya, JM, et al. (2006) Ecological networks and their fragility. Nature 442, 259-264.
  1. Outland, K. (2010) Who’s afraid of the big bad wolf? The Yellowstone wolves controversy. [Online]. [Accessed 10 November 2014]. Available from:
  1. Platten, S. and Henfrey, T. (2009) The Cultural Keystone Concept: Insights from Ecological Anthropology. Human Ecology 37, 491-500.
  1. Ripple, WJ, and Breschetta, RL. (2004) Wolves, elk, willows, and trophic cascades in the upper Gallatin Range in Southwester Montana, USA. Forest Ecology and Management 200, 161–18.
  1. Schulp, CJE, et a (2014) Quantifying and mapping ecosystem services: Demand and supply of pollination in the European Union. Ecological Indicators 36, 131-141.
  1. Soulé, ME, et al. (2005) Strongly interacting species: conservation policy, management, and ethics. Bioscience 55, 168-176.
  1. Steneck, RS, et al. (2002) Kelp forest ecosystems: biodiversity, stability, resilience and future. Environmental Conservation, 29, 436-459.
  1. Stirling, I, and McEwan, EH. (1975) Calorific value of whole ringed seals (Phoca Hispida) in relation to polar bear (Ursus Maritimus) ecology and hunting and behaviour. Canadian Journal of Zoology-Revue Canadienne De Zoologie 53, 1021-1027.
  1. Techera, EJ, and Klein, N. (2007) Sharks: Conservation, Governance and Management. Earthscan, 155-175.
  1. Trail, PW. (2007) African hornbills: keystone species threatened by habitat loss, hunting and international trade. Ostrich 78, 609-613.
  1. Worm, B, and Myers, RA. (2003). Meta-analysis of cod-shrimp interactions reveals top-down control in oceanic food webs. Ecology 84, 162-173.