Tag Archives: hunting

Predators Under Nightlights

This is a guest post by Dr. Mark Ditmer.

Streetlights like these have meant that for some animals, hiding in the dark is now increasingly difficult (Image Credit: ME Stoner, CC BY 2.0, Image Cropped)

Artificial nightlight alters the predator–prey dynamics of an apex carnivore (2020) Ditmer et al., Ecography, https://doi.org/10.1111/ecog.05251

The Crux

The earth is no longer dark at night – artificial lighting has degraded the dark nighttime conditions that many species have evolved with throughout their evolutionary history. This change is only accelerating, with human expansion and intensity of radiance continuing to increase annually. We already know that elevated light levels can disrupt ecological processes like pollination or migration, as well as have a litany of negative effects on individual species, from physiological stress to predation risk. But it’s hard to get an idea of how the increase in ‘light pollution’ affects free-roaming wildlife, especially large mammals, and especially at scales relevant for making conservation policy.

In areas like the American west, the rapid growth of urban areas and the accompanying spread of light pollution create a rapidly changing ecosystem, one that sees many conflicts between humans and wildlife. One particularly species of particular interest is the mule deer (Odocoileus hemionus), which seeks out sources of forage on the edges of and within towns and cities (e.g. parks, farms), especially in arid regions. The primary predator of mule deer – the cougar (Puma concolor) – also navigates and hunts near human development where their prey congregate, but tend to avoid human presence more so than deer.

Today’s authors wanted to assess how artificial lighting, both where it occurs and its intensity, can shape the behaviors and predator-prey interactions of these species across the American West ranging from the edges of bright urban regions, such as Salt Lake City (Utah) and Reno (Nevada), to areas receiving minimal light pollution like Grand Canyon National Park.

What They Did

The authors used a massive dataset that included GPS-locations from 263 mule deer, 56 cougars, and 1,562 locations where cougars successfully killed mule deer. The resulting location data were combined with estimates of anthropogenic light pollution (more on this in Did You Know?).

Several different analyses were performed on the combined light and GPS-location data, along with other variables representing environmental (e.g., snow cover, land cover, terrain) and human factors (e.g., distance to roads, housing density). The aim was to figure out whether A) light has any influence on the behavior of each species, B) cougars avoid areas with high light pollution, allowing deer to forage freely wherever and whenever they want (the ‘predator shield hypothesis’), or C) cougars exploit the higher densities of deer seeking forage around areas with elevated light pollution (e.g., parks, golf courses, agriculture; the ‘ecological trap hypothesis’).

Did You Know: A Space Agency’s Ecological Impact

In this study we used remote sensing data to determine the amount of light pollution in a given environment. Yet the sensors only pick up the total amount of light, and can’t tell us what is a product of our activity and what is a natural source of light. To separate the two, we used light data which was recently developed by the U.S. National Aeronautics and Space Administration (NASA). This dataset removes the contributions of natural sources of light (e.g., moonlight, fire, atmospheric spray) from our data and results in values of just the human-created nighttime light emissions.

What They Found

The behaviors of both species changed greatly with levels of light pollution, as did the predation risk for deer. The behaviour changed across different scales as well. Cougars killed deer in study sites with the high amounts of light pollution, but within those sites (e.g., edge of Salt Lake City, Utah) cougars selected to hunt and kill in the relatively darkest locations. In contrast, in the darker study areas, cougars killed deer in areas with the relatively more light pollution than the surrounding area. However, even though cougars killed deer in the darkest spots within the bright urban interface, those locations generally had much higher levels of light pollution than the brightest kill sites in the low light pollution study areas.

The study found that cougars made kills in bright regions, but generally only within the darker parts of those regions (Image Credit: ME Stoner, CC BY 2.0)

Deer living in brighter urban areas tended to forage at night, potentially to avoid direct human interactions. This shift might have benefited deer by avoiding humans, but as they sought out more natural and dark locations in these areas, cougars would wait in ambush.

In the end, the authors concluded that their findings fell in a gray zone between the predator shield and ecological trap hypotheses dependent on scale. Areas with high levels of light and subsequent human activities provide excellent foraging opportunities for ungulates (as this study measured as well), but adaptable predators can follow and take advantage – at least in environments that they feel are safe enough.

Problems

This is an observational study, so it’s hard to fully tease apart what effects are driven by light and what are driven by other human factors. We did our best to account for the other more traditional sources of the human footprint, reporting effect sizes for each, but there’s always a chance we’re attributing some effects to light pollution that could be caused by some other aspect of our presence.

So What?

Work like this shines a light on (pun intended) how different species will respond to the ongoing urbanization trends humans are driving in much of the planet.

Although many wildlife ecology studies consider various human alterations to habitats and the consequent changes in animal behavior, most studies fail to consider the sensory environment and the pollutants (e.g., noise, light) that can impact wildlife populations in their analyses. How wildlife use an ecosystem can impact everything from human-wildlife interactions to pulses of nutrients to the soil based on shifting areas of kill sites/carcasses.

Dr. Mark Ditmer is a post-doctoral researcher at the Centre for Human-Carnivore Co-Existence and Wittemyer Lab at Colorado State University. You can read more about him at his profile here or follow him on Twitter @MDitmer.

Ecological Fortification

When we think of wolves, and more specifically what they like to eat, the first thing that comes to mind is often the image of a pack tirelessly hunting down large ungulates. It’s a high octane, endurance race to the death – one which also involves some tag teaming.

Well it turns out these endurance specialists are able to trade in their usual cursorial (fancy word for running your prey down) approach to hunting for a more ambush (less fancy word for sitting very still and jumping out on something) style depending on their choice of prey. Researchers found that when wolves turned their eyes to other prey types such as beavers, they adopted a sit-and-wait tactic more commonly seen in cats. They were often even observed waiting downwind so as to avoid the beavers keen sense of smell.

It’s cool to know that we are still learning new things about these charismatic and well studied animals – in this case their ability to ‘activate’ ambush mode should the need arrive.

Tanya Strydom is a PhD student at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.

Can Humans and Wild Ungulates Live Together in a European Landscape?

Guest post by Benjamin Cretois (Image Credit: Wer Mei, CC BY 2.0)

The challenges and opportunities of coexisting with wild ungulates in the human-dominated landscapes of Europe’s Anthropocene (2020) Linnell, Cretois et al., Biological Conservation, https://doi.org/10.1016/j.biocon.2020.108500

The Crux

The “land sparing vs land sharing” debate is not new to wildlife conservation and is more relevant now than ever. Land sparing entails creating areas distinctly for wildlife, commonly referred to as Protected Areas. The science of spared landscape is well developed and its principles were fundamental to early conservation biology. On the other hand, the confinement of wildlife into human-free area is possible on a very limited in a highly anthropogenic landscape like Europe. Hence, the coexistence movement, which requires both wildlife and humans to share their landscape, leading to a wide range of interactions between the too. This is especially true when it comes to charismatic large mammals including large carnivores and ungulates, whose range has large overlaps with ours.

We wanted to summarise the knowledge on wild ungulate distributions and examine wild ungulate-human interactions. Ungulates are quite varied in Europe, and this study included species such as the wild boar, European bison, moose and roe deer.

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A Secret Ecosystem Under the Snow: The Winter World of the Subnivium

This fox has tracked down his next meal by listening for sounds in the subnivium. Image Credit: Yellowstone National Park, Public Domain Mark 1.0, Image Cropped.

Sometimes the hardest places to access are the most interesting places to study. Take the subnivium, a temporary ecosystem that forms each winter in the small space between the snowpack and the ground.

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Fredrik Widemo: The Manifold Conflicts Behind the Hunting Industry

Image Credit: USFWS Endangered Species, CC BY 2.0, Image Cropped

Rewilding is a tricky business. Bringing back species that once roamed a country as their native land may seem like a worthy cause, but it is often fraught with conflict. People don’t want predators threatening their safety, or herbivores destroying their crops. Rural vs. urban tensions come into play. Local and federal politics get thrown into the mix.

With that in mind, I sat down with Associate Professor Fredrik Widemo, currently a Senior lecturer with the Swedish University of Agricultural Sciences. Fredrik has previously worked at both the Swedish Association for Hunting and Wildlife Management (where he was the Director of Science) and the Swedish Biodiversity Centre. We explored some of the complexities behind the rewilding of wolves and its effects on the hunting and forestry industries in Sweden.

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Ecology of the GoT Dragons

Image Credit: Game of Thrones, 2019

Adam and Sam talk macroecology and that’s pretty much it. How small would these dragons be? It’s very anti-climactic. We’ll do a supplemental later. Also SPOILERS. Though as we were a week behind, there’s some stuff that is currently incorrect re: the current status of the GoT dragons. Spoilers.

04:02 – Everyone’s Favourite Dragons
13:15 – The Ecology of the Dragons
40:13 – Balerion the Big Boi vs. The US Military

And as usual, you can check out last week’s podcast on the physiology of these flappy flaps flaps below.

Episode 3: A Quiet Place

Image Credit: A Quiet Place, 2018, Image Cropped

We dive into the quiet B O I S from 2018’s A Quiet Place. Dave think lions are from Antarctica, Adam gets too damn excited by Alligator gar and Sam’s stepson ruins the episode.

Movie History/Movie Any Good – 6:28
Quiet Physiology – 17:16
Quiet Ecology – 44:40
A Quiet BOI vs. Dwight Schrute – 1:09:46

Listen to the full episode below. For a more detailed breakdown, head over to Cinematica Animalia.

Bringing Back the Wolverine

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area (Image Credit: Vojtěch Zavadil, CC BY-SA 3.0, Image Cropped)

Paying for an Endangered Predator Leads to Population Recovery (2015) Persson et al., Conservation Letters, https://doi.org/10.1111/conl.12171

The Crux

Humans have a long history of driving dangerous predators out of their backyard. Wolves and wolverines have been driven out of different parts of Europe at different points in history at the behest of farmers looking to protect their livelihood, and the Tasmanian Tiger was driven to extinction for the same reason. But with the realisation that these predators bring enormous ecosystem benefits, governments have been searching for ways to bring about co-existence between predators and locals.

This study looks at a scheme introduced by a Swedish government in 1996, where reindeer herders had previously been compensated for any wolverine related losses. The new scheme introduced compensation for successful wolverine reproductions in the area. Persson et al. decided to have a look at how it fared.

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Rewilding

The reintroduction of wolves into Norway continues to incite controversy

Image Credit: Doug Smith, NPS, Public Domain, Image Cropped

Can you imagine a wild Scandinavia filled with untamed forests, wild boar, and large predators (and maybe a stray Viking)? This is the dream of some scientists advocating for the reintroduction of species once found in Europe that have either been hunted to extinction or driven out by intensive agriculture. The reintroduction of species, particularly animals dubbed “ecosystem engineers” such as beavers and large carnivores are of special interest due to the positive landscape-level effects of these species.

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The Wild Boar

The wild boar, originally native to Norway, is now making a return after being wiped out. So how do the locals feel? (Image Credit: Richard BartzCC BY-SA 2.5, Image Cropped)

In this series we’ll be mainly dealing with alien species invading new parts of the world. However it’s important to recognise that not all invasive species are alien to the territories they invade, and not all invasive species are unanimously unwelcome. Today, we look at a species that is now returning to its former native territory, and which is being welcomed back by some.

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