Category Archives: bats

Urban Ecology and Impacts on Bats

Okay so bats might not seem frightfully important to us…surely they’re nothing more than flying rats? You’d be mistaken! These incredible mammal species are a highly evolved flying and echolocating species- the only ones to do so. They ensure our skies aren’t ridden with biting insects, prevent crop damage, provide medicine in the form of draculin, give vision to the blind and lets be honest, MAKE Halloween! I conducted 10 months research on them a year ago, and here’s what I found out about how our urban lifestyle is impacting them in the UK.

Importance and impacts of an urban landscape on bats: Urban foraging

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, it is of vital importance to study the effects of particular habitat features on bats, as each specie uses the landscape differently (Altringham, 2011, Coleman & Barcley, 2011).

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 & Ancillotto, 2014; Stone et al., 2011).

bats urban 1

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).

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). Urbanization may result in greater competition between the synurbic and less well adapted species. Arlettaz et al., (2000) suggested that the decline of 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 normally avoided by the lesser horseshoe bat (Warren et al., 2002; Lacoeuilhe et al.,  2014).

Water in urban areas

Bats are vulnerable to evaporative water loss as a consequence of their morphology and large surface area to volume ratio (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 can attract large numbers of bats to urban and modified sites (Altringham, 2011).

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).

So this Halloween, cast a glance into the skies at night and spare a thought for this remarkable little evolutionary quirk of nature…

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!

http://www.bigbatmap.org/pages/help-count-bats.html

The value of bats

cute bats
Apart from being amazingly cute!

Exactly a year ago today I conducted my research on British bats around North and West Yorkshire regarding their habitat selectivity across multiple scales in rural and urban environments. I still can’t believe how fast it’s all gone in the past 10 months! I will be posting up some articles on exactly what I did and how you can also get involved with conserving these fascinating little mammals of ours too, but first I want to tell you WHY bats are so important to us all.

p.pyg photo
Just hangin’ around… Pipistrellus pipistrellus (Common Pipistrelle)

Apart from justifying the value of bats in terms of their diverse nature and unique evolutionary history which has lead to the only powered flight seen in mammals (Fenton et al, 1997), bats provide a range of ecosystem services and benefits to both the environment and humans (Altringham, 2011). The Brazilian-free tailed bat provides one of the largest-scale suppressions of insect pests in the world (Kunz, 1989). During their migration northwards each spring, Tadarida brasiliensis forage on cotton bollworms, saving the US economy over $23 billion dollars in terms of preventative damage to cotton and the reduced cost of less pesticide use (Cleveland et al 2006).

tad maps bats

In Asian markets, over 70% of the fruit sold is pollinated or seed dispersed by bats, in particular the Durian fruit which is worth $2 billion (Kasso & Balakrishnan, 2013, Altringham, 2011). The alcoholic beverage, Tequila is derived from the Agave tequilana and is pollinated by the lesser-long-nosed bat, providing a source of income of for many Mexicans (Kunz et al, 2012). Guano is a source of high concentrations of phosphorus and nitrogen, which is one of the primary limiting nutrients of plant life. Deuchamp et al (2009) studied the potential benefits of the ‘pepper shaker-effect,’ a hypothesis where bats flying from nutrient-rich regions to nutrient-poor habitats, redistribute the guano and act as a mobile fertiliser. Several countries sell guano as fertilisers and can be a main source of income in poorer regions (Altringham, 2011).

lesser-long-nosed-bat-wide
The lesser-long-nosed-bat hovering over a cactus flower.

tequila-shot-cinco-de-mayo-her-sweat

bat for powerpoint

Ecotourism also boost the economy, for example as seen in Congress Avenue, Texas which generates $12 million annually (Pennisi et al, 2004). Medicine is also derived from the Vampire bat’s salivary enzyme, desmoteplase which acts as an anticoagulant for post-ischemic stroke patients (Furlan et al, 2006). This was initially trialled on mice in 2003, and was found to extend the time required to administer tissue plasminogen activator during the post-stroke period from 3 to 9 hours (Schleuning et al, 2008).

desmoteplase
Molecular structure of desmoteplase.

vamps

Other aspects of bat biology providing benefits to humans include the development of the ©UltraCane, a device that enables the blind to detect oncoming objects. Developed by researchers at the University of Leeds, it was based on the echolocation calls of bats and has helped thousands of visually impaired people (Scheggi et al, 2014).

ultracane
The Ultracane

Also mentioned is their value as bioindicators of the overall health of the ecosystem, which can be seen with their importance in ecological networks and high trophic level, if removed, cumulative and rippling effects can be seen lower down trophic cascades (Jones et al, 2009).

I hope you can see how incredible these little mammals are, and stay tuned to find out about the amazing world of bats in future posts!

Check out our Ecosapien video on bats:

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