Camera trap

Large mammals at Mt. Kilimanjaro: the importance of resource availability and protected areas

/ Journal of Animal Ecology / 1 Comment

This blog post is provided by Friederike Gebert from the University of Würzburg and tells the #StoryBehindThePaper for her article  Primary productivity and habitat protection predict elevational species richness and community biomass of large mammals on Mt. Kilimanjaro which has been shortlisted for the 2019 Elton Prize.

Mountains are biodiversity hotspots and prior areas for conservation. Even though elevational gradients belong to the best described patterns in ecology, their drivers remain controversial until today. We wanted to contribute to this discourse by investigating the distribution and predictors of large mammals on Mt. Kilimanjaro, the highest free-standing mountain in the world. Despite their immense functional and cultural importance, so far, large mammals have been neglected in studies on elevational diversity patterns.

However, at the beginning of our research project on Mt. Kilimanjaro, we did not have mammals as focal organisms in mind, but a group of organisms that is very different, yet closely related to mammals: dung beetles. Dung beetles are important decomposers and are largely coprophagous, meaning they feed and nest in mammalian dung. Originally, we were particularly interested in the factors behind the patterns of dung beetle diversity on Mt. Kilimanjaro. Among other factors, we wanted to test the availability of resources as a driver of dung beetle diversity. This is where mammals first came into the picture – instead of taking primary productivity as a proxy for resource availability for dung beetles, as do most studies, we wanted to have an accurate measure of resources available for dung beetles. To this end, we recorded mammals with camera traps and calculated defecation from mammal biomass data. In the course of analysing the results for the dung beetle study, now published in the Journal of Biogeography, we realized that we obtained a very valuable mammal data set, which is why we decided to publish our results in the Journal of Animal Ecology.

 

For documenting mammals on Mt. Kilimanjaro, we put up five camera traps each on 66 study plots, spanning an elevational gradient from 870 m to 4500 m. The study plots represented the major natural and anthropogenic habitats that can be found on the southern slopes of the mountain. They ranged from habitats such as savannah and maize fields at low elevations over lower montane forest and Chagga homegardens at mid elevations, to Mt. Kilimanjaro National Park, which protects all habitats above 1800 m and encompasses several natural and disturbed forest habitats and afro-alpine shrub vegetation. The camera traps remained in the field for two weeks. We collected a daunting 80.000 film snippets, each lasting 20 seconds. I started by looking at the film snippets from the savannah and was on the verge of getting desperate because I had watched thousands of videos already just showing moving grass, without trace of any mammal, when I finally spotted the first baboon. In the end, around 1600 videos did actually show mammals. In total, we recorded 33 wild mammal species and five domestic mammals. Apart from camera traps, we also used transect walks to document mammal faeces – we reported 176 dung samples.

We recorded common species like the Common Duiker and the Zanzibar Syke’s Monkey, but also species such as the Eastern Tree Hyrax, the Lesser Kudu and the Plains Zebra, which are categorized as threatened, and the Leopard, which is listed as vulnerable. Our biggest highlight was that we filmed the Abbott’s Duiker for the first time on Mt. Kilimanjaro. The Abbott’s Duiker is an elusive montane forest species endemic to Tanzania; it is restricted to a few isolated mountains in East and South Tanzania and listed as endangered in the IUCN red list. Prominent features of this duiker are the glossy, nearly black colour and the russet tuft between the horns. The first photograph of this species was taken as recently as 2003 and in 2013, the first videos were shot in the Udzungwa Mountains, the southernmost block of the Eastern Arc Mountains. Previously, the distribution of the Abbott’s Duiker on Mt. Kilimanjaro was hardly known – in the present study, we filmed the Abbott’s Duiker on 105 occasions at eleven study sites, ranging in altitude from 1920 to 3849 m. This high occurrence of the Abbott’s Duiker makes us suggest that Mt. Kilimanjaro could be another stronghold of this species apart from the Udzungwa Mountains. We are very proud to be the first ever to film an Abbott’s Duiker pair and a male trying to mate.

 

We found that mammal diversity and community biomass showed a hump-shaped pattern along elevation with a peak at 2500 m. However, when we only considered protected study plots – two savannah study plots inside a game reserve and Mt. Kilimanjaro National Park – the distribution of mammal species richness shifted to a low-elevation plateau, peaking at 1500 m. This result was mainly caused by the largest mammals, like the Lesser Kudu and the Plains Zebra, which were absent from unprotected study plots and only occurred in protected areas. As potential drivers of mammal diversity, we considered temperature, resource availability, area and human impact. Mammal diversity at Mt. Kilimanjaro was mainly predicted by primary productivity – our measure of resource availability for mammals –, climate and the protection status of study plots. The former driver lends support to the ‘energy-richness’ or ‘species-energy hypothesis’, which states that highly productive ecosystems harbour abundant resources, so that more and larger populations can persist than in less productive ecosystems. While the effect of primary productivity on mammal diversity was direct, there was both a smaller direct and stronger indirect effect of temperature, mediated via resource availability. The latter driver, the protection status of study plots, has huge implications for conservation. Large mammals perform key roles in ecosystems and their loss from unprotected habitats, for example through habitat destruction, hunting and retaliatory killing, will likely have negative repercussions on species communities and mammal-mediated ecosystem services, such as the maintenance of habitat heterogeneity. From a conservation point of view, there is no alternative to the designation, maintenance and expansion of protected areas to preserve mammal diversity in the long term.

 

Urbanization alters predator‐avoidance behaviours

/ Sarah Marley / Leave a comment

Urbanisation is changing the natural landscape at a global scale. This obviously alters habitat structures, but what is the influence on predator-prey dynamics? A recent paper in the Journal of Animal Ecology studied two urban prey species to examine whether urbanisation changed their predator-avoidance behaviour. Lead author Dr Travis Gallo, an Urban Wildlife Postdoctoral Researcher at the Urban Wildlife Institute, Lincoln Park Zoo, tells us more. 

It’s easy to recognize that urban environments are quite different from the rural or natural landscapes ecologists have historically studied. Thus, urban ecologist have long stated that traditional ecological principles should be adjusted or fine-tuned to better fit urban ecosystems. For example, continuously maintained landscapes in cities stabilize primary productivity and reduce the ‘dynamic’ part of the well-studied principles of top-down and bottom-up trophic dynamics. Along those same lines, we became interested in the role that cities and their unique characteristics play in predator-prey dynamics.

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A coyote out in the open in Chicago (Photo: Julie Fuller)

In a study recently published in the Journal of Animal Ecology, we explored predator-avoidance behaviors of two common mammal species – eastern cottontail (Sylvilagus floridanus) and white-tailed deer (Odocoileus virginianus) in the highly urbanized landscape of Chicago, IL USA. Contrary to what one might expect, we found that coyotes (Canis latrans) – a natural predator – had little influence on predator-avoidance behaviors of either species in the more urbanized areas of Chicago.

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White-tailed deer doe and fawn (Photo: Urban Wildlife Institute)

But first let’s step back and offer a little context. Typically, the presence of a predator influences the distribution and behavior of prey species. One might expect that prey, if able, would first and foremost avoid habitat patches that contain predators. But our expectations for this outcome were derived from more natural systems — so how might this relationship change in a city? Habitat patches in urban environments are typically spaced far apart and embedded in a matrix of houses, businesses, and roads. The roads and buildings between habitat patches could restrict an animal’s ability to move between them. As a result, it may be all the more difficult for prey to ‘pack up and move’ if they so happen to encounter a predator. Therefore, we predicted that urban prey might be forced to occupy the same habitat patches as predators. If this were the case, we predicted that prey would change their daily activity schedules or increase their vigilance to avoid interactions with predators. But again, human development and human activity in and around an urban habitat patch might alter a species ability to perform such predator-avoidance behaviors.

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Remotely-triggered wildlife cameras around Chicago allowed a sneak peek into predator-prey dynamics of local wildlife (Photo: Urban Wildlife Institute)

Using photos collected from over 100 remotely triggered wildlife cameras placed across the greater Chicago region, we first assessed whether deer and cottontails were more likely to occupy the same habitat patches as coyotes – or were they avoiding them across the landscape? Additionally, we used the time of day each picture was taken to explore whether deer and cottontails changed their daily activity patterns when coyotes were present within a habitat patch. And finally, in each picture of deer and cottontail we identified whether the individual animal had their head up in a vigilance posture or down in foraging posture, and used that information to assess whether the presence of coyotes increased their rate of vigilance.

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An eastern cottontail displaying vigilance (Photo: Urban Wildlife Institute)

 

Contrary to our prediction – that prey species would likely be constrained to the same habitat patch as coyotes – we found no evidence of spatial aggregation, nor did we find any evidence of spatial avoidance. Both deer and cottontails were spatially distributed independent of where coyotes were present. Additionally, we found that neither species changed their daily activity schedules when coyotes were present. Our most interesting finding was that cottontails had their highest rates of vigilance when coyotes were absent from the most urban sites. Even when coyotes had a low probability of being at a site, cottontails were still on their toes! In Chicago, these highly urban habitat patches (e.g., city parks, golf courses, cemeteries) are often visited by people and in many cases people with their pets (sometimes untethered). While these urban green spaces may provide a refuge from coyote (i.e. a human-shield effect), they likely come with tradeoffs in the form of increased interactions with humans and their pets. As a result, their vigilance rates are high in urban areas even when coyotes are not around. Conversely, as sites became less urban we began to see a shift back to expected vigilance behaviors, and rabbits were more vigilant when coyotes were present in the less urban areas.

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Cemetaries are highly-urban habitat patches, regularly visited by people (Photo: Urban Wildlife Institute)

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As well as people, wildlife also come across pets (Photo: Urban Wildlife Institute)

These results indicate that urban ecosystems are still fear driven systems, but perhaps, the fear inducing agents are now anthropogenic in nature. Traditionally we think of predator-prey dynamics in the context of two interactions – predators and prey. But in urban ecosystems we must begin to think of it as a three-player game – predators, prey, and people. Thus, we should begin to explicitly consider people in our ecological equations – especially in urban ecosystems. Doing so will improve our predictions, advance our understanding of urban ecology, and increase our ability to conserve biodiversity on an urbanizing planet.

More Info:

Gallo et al. (2019) Urbanization alters predator‐avoidance behaviours. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.12967

Estimating Species Populations – a critical step in understanding ecological processes

/ Sarah Marley / Leave a comment

Understanding the size of animal populations is necessary – but also extremely challenging. Andrea Campos Candela, a PhD student with the Fish Ecology Lab in the Mediterranean Institute for Advanced Studies (IMEDEA-CSIC) talks us through this problem.

“How many animals are there?

Understanding ecological processes and the dynamics of wild animal populations is dependent on our answer to such seemingly simple question.  Further, recognizing changes in population over time and geographically or due to environmental events, human impacts and even the climate change effects is critical to understanding ecological processes.  Despite its great relevance, addressing this fundamental scientific issue is still a challenge in ecology.

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Underwater image sampling is wide spreading in marine ecology (Image: Pablo Arechavala López)

Animal density is the number of animals in a unit area. Discovering this relies on going out to the countryside or under the sea and counting, counting and counting. However, “how to count” remains a long-standing issue. Since the beginning of ecological science, the search for methods to count faster and better, allowing robust statistical analysis has arisen many intriguing scientific debates.

Among other factors, animals do not sit still. Counting moving animals is no easy task but challenging, even without considering limited visibility or the desire for continuous, remote, repeatable monitoring. By using camera traps in terrestrial ecosystems, or baited cameras underwater, we may make robust, verifiable observations. Yet still, our data represents a limited snapshot of the environment.

However, one property of animal behavior may help in such a challenge: their Home Range. Animals typically move in space within certain limits of what we interpret as their territory or their proper “home” or Home Range. This behavior occurs broadly among mammals, reptiles, birds, and fish. Mathematically, we consider this home range ‘stationary’ in time and space. As such, the likelihood of discovering an individual at a certain point decreases with the distance of our point of observation from the centre of its Home Range. Given how widespread this behavior is among different taxa we wondered how such a stationary property of the movement could be used in estimating animal absolute densities.

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Camera trapping is an extended method for the study of terrestrial mammals (Image: Gonzalo Mucientes).

However, we still need data. What kind of? How do we collect it? Taking advantage of modern technology, managers and scientists have gained powerful tools for improving terrestrial and aquatic wildlife surveys with the recent technological advances in wildlife video recording. Using unmanned aerial vehicles (UAVs) we can monitor a wide range of wildlife, including birds, terrestrial and aquatic mammals. In aquatic systems, miniaturization of underwater video recording devices and the installation of cabled video observatories have broadened the remote, long-term and high frequency monitoring of fish and their environments. Meanwhile, onshore, camera devices triggered by the movement of animals (camera trapping) increase the sample time for mammals’ studies and therefore the opportunities to improve our knowledge of how many animals there are.

Combining the mathematical properties of the Home Range behaviour and the count of animals in each frame of a camera record, we can estimate the density of the animals with greater certainty. Recording a period of time long enough for animals to visit their whole Home Range (which is, talking statistically, when the stationary probability density function of Home Range centres can be recovered), the absolute animal density can be robustly estimated from averaged counts across independent frames divided by the area surveyed by each camera. Testing our hypothesis, we mathematically simulated the movement and population density of various taxa, including birds, reptiles, mammals and fish, from different terrestrial and aquatic environments. The results of our work show that this method predicts the density of species across taxa with a very little error!

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Andrea undertaking a periodic maintenance check of Sub-Eye, the underwater-cabled coastal observatory in Port d’Andratx, Balearic Islands. (Image: Pablo Arechavala López).

However, we do not think that this is the end of the road. Our team continues working to improve the mathematical development and application of our model. We aim to answer, for instance, what would happen when the detection of the animal is not hundred percent. We hope this new mathematical model, together with the new opportunities offered by the recent technological development of video cameras, will help us to solve this classic enigma of the ecology, but it will also contribute to the conservation of many threatened species in our ecosystems.

Deriving this new formula overcomes some former skepticisms in ecology, such as the fact that recounting the same individual several times could be a problem for estimating abundances. Therefore, we may revisit the classical problem of ecology from a new perspective; how many fish are there really in our seas? How many reptiles are there in our mountains? How many birds in our forests? How many animals are there in our study areas?  We still have a lot of exciting work ahead of us!!

More info:

Campos-Candela, A., Palmer, M., Balle, S., and Alós, J. (2017). A camera-based method for estimating absolute density in animals displaying home range behaviour. Journal of Animal Ecology. DOI: 10.1111/1365-2656.12787

Spatial overlap in a solitary predator

/ Journal of Animal Ecology / 1 Comment
F97, a subadult female raised by F61. Photograph by Patrick Lendrum / Panthera.

F97, a subadult female raised by F61. Photograph by Patrick Lendrum / Panthera.

F61 and F51, adult female cougars (Puma concolor), also called mountain lions, were very nearly the same age when they gave birth to their first litters of kittens within a month of each other in 2011. The pair of big cats were neighbors in adjacent and overlapping home ranges in the Bridger-Teton National Forest, east of Grand Teton National Park in northwest Wyoming, USA.

A well-placed motion-triggered camera caught a fortuitous image of F61 and F51 spending time together in early 2012, accompanied by their four kittens (1 from F61, 3 from F51). It sparked great discussion among our team, many of whom were convinced they must be close relatives, perhaps sisters. Indeed, prevailing theory supported the idea that close kin were more likely to be close to each other and tolerant of one other. Thus, it just made sense that the two cats would be kin. At the time, however, we did not know the genetic relatedness of cougars in our study, except of course, kittens born to females we were tracking. Continue reading →