Tag Archives: predator

My Enemy is Not the Enemy of My Other Enemy

Do predators keep prey healthy or make them sicker? A meta- analysis (2022) Richards et al., Ecology Letters, https://doi.org/10.1111/ele.13919

Image credit: Angah hfz, CC BY-SA 4.0, via Wikimedia Commons

The Crux

Ecology is all about understanding how the various parts of the natural world interact with one another. While we tend to think about things like predators, competitors, and parasites as separate entities that have their own effects, it is important to remember that these species interactions can interact with one another. Such interactions will have implications for the dynamics of natural populations.

Of interest is how predators and parasites interact with one another through their shared resources, prey/host species. Specifically, the Healthy Herds Hypothesis (HHH, see Did You Know?) predicts that predators reduce parasitism within the populations of their prey. While the HHH was based on a mathematical model, other theoretical models predict a range of effects, from predators decreasing parasitism to actually increasing parasitism. Because the empirical results from experimental studies show similar variation in their results, today’s authors wanted to determine if there is indeed a consistent, overall effect of predators on the parasitism of their prey.

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The Guilt of One Shark: The History of the “Rogue Shark” Theory

Image Credit: Sharkcrew, CC BY-SA 4.0, Image Cropped

In February 2022, a British swimmer was killed by a great white shark (Carcharadon carcharias) near Sydney, Australia. Unsurprisingly, this gained significant media attention. State authorities launched a search for the culprit, with the aim of culling/relocating it away from people. This plan would seem, on the surface, to make perfect sense – shark ate human, make it go away. Yet this logic is largely based on a widespread misconception, and an outdated theory that science has long since abandoned.

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The Ramifications of Clashes Between Wolves and Bears

Image Credit: Yellowstone National Park, CC BY 2.0, Image Cropped

Of wolves and bears: Seasonal drivers of interference and exploitation competition between apex predators (2021) Tallian et al., Ecological Monographs, https://doi.org/10.1002/ecm.1498

The Crux

I’ve written a lot about our relationship with top predators like bears and wolves on Ecology for the Masses, but their relationship with each other is also capable of having a big impact on their surroundings. When bears live in the same regions as wolves, predation levels are generally higher, but how much higher really depends on how much competition takes place between the two species.

Competition can take two forms out in the wild: interference competition, in which a bear might drive wolves away from a kill they’ve made, and exploitation competition, in which wolves have to search longer because bears have reduced the number of prey species in their area. Since both bears (through hibernation) and their prey species (through fixed mating cycles) vary in their behaviour throughout the year, could the type of competition that wolves face vary throughout the year as well? That’s what today’s authors wanted to find out.

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The idea that we should live in a predator and stress free (for herbivores) has been doing the rounds again these last few days. Apart form it being a very-bad-no-good idea to remove all predators from a system its also easy to forget that herbivores can be just as big of a source of stress for other herbivores as the threat of predation.

I mean we know that herbivores sometimes order off of the meat menu (Omnomnomivores anyone?), can bully smaller species off of/away from resources, and can be a general menace to society ‘just because’. To put it simply there is always going to be something causing an individual some type of stress out there (even from their own species). Saying that predators are the problem is not a sustainable way of thinking, and is also an overly simplistic view of ‘predation’. From the view of a plant herbivores are predators are they not?

For an earlier take on when this issue cropped up last year, check out the link below.

Read More: An Attempt To Understand Painlessly Killing Predators

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.

The Dog Who Cried Wolf: Promoting Co-Existence With Carnivores Through Livestock Guarding Dogs

Centuries of folklore have made us wary of carnivores. Whether it’s the Big Bad Wolf, the Tsavo Man-Eaters, or the dingo that stole Lindy Chamberlain’s baby, horrifying tales of rare events have made us uneasy about them. Yet as ecologists constantly espouse, they are integral parts of any ecosystem, and the gradual return of wolves to many parts of the northern hemisphere represents a huge boost for biodiversity.

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Can We Figure Out Where Human-Wolf Conflicts Are The Most Likely?

Image Credit: Isster17, CC BY-SA 4.0, Image Cropped

Men and wolves: Anthropogenic causes are an important driver of wolf mortality in human-dominated landscapes in Italy (2021) Musto et al., Global Ecology and Conservation, https://doi.org/10.1016/j.gecco.2021.e01892

The Crux

The reintroduction of wolves into many regions in the Northern Hemisphere is massively controversial, and even a constant parliamentary debate in some countries. There are no doubts that wolves bring considerable benefits to local biodiversity wherever they are reintroduced, but there are also no doubts that their reintroduction is met with trepidation by the local human populace.

That makes figuring out where conflicts are likely to arise and wolves and likely to be shot, poisoned, or hit by a car really important. If we can figure out where wolves are most likely to be killed, it can help conservationists figure out where their populations need the most attention, and where outreach to local farmers could prevent further conflicts. That’s what today’s authors wanted to figure out.

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Small Creatures, Large Effects

Arthropod predation of vertebrates structures trophic dynamics in island ecosystems (2021) Halpin et al., The American Naturalist, https://doi.org/10.1086/715702

Image credit: Bernard Dupont, CC BY-SA 2.0, via Wikimedia Commons

The Crux

Predator-prey dynamics are (I think) the most well-known species interaction out there. Not everyone is a scientist, but almost everyone has seen an image of a cheetah running down a gazelle, a great white shark exploding out of the water as it hammers a seal from below, or wolves teaming up on a much larger herbivore.

These interactions are not only fascinating and captivating, they are also key to structuring communities. For example, the damselflies that I worked with during my PhD occur in two different kinds of lakes: fish lakes and dragonfly lakes. The type of predator alters the lake significantly: damselflies that live in fish lakes are adapted to “hide” from their fish predators by not moving. Not moving in a dragonfly lake means that a dragonfly will eat you.

Though these interactions have been (justifiably) studied to an extreme extent, there are still knowledge gaps out there. Of interest for today’s study is the effect of invertebrate predators on vertebrate prey. While these invertebrate predator/vertebrate prey interactions have been studied in marine and freshwater environments, little work has been conducted in terrestrial systems. This is especially hard to do with invertebrate predators of vertebrate prey, because such predators tend to be hard to find, nocturnal, and they also hunt in more “concealed” environments like leaf litter. To overcome these challenges, today’s authors utilized the Phillip Island centipede (Cormocephalus coynei, which is NOT the centipede featured in this post’s image) and stable isotope analyses (see Did You Know) to understand how invertebrate predators structure food web dynamics.

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Bear-ly Moving

It’s Fat Bear Week!

An annual (as chosen by the fans) competition to find the bear who had the most summer gains in preparation for their winter downtime. As they won’t be coming out to forage during the winter months, the bears need to spend the summer months not only regaining that which they lost the previous winter but also shoring up their reserves for the coming winter. This means finding foods that are rich (fatty) and plentiful – salmon happen to tick both of these boxes and are one of the highly sought after snacks over the summer time.

Read More: Fat Bear Week

Check out the before and after shots of these cuddly teddies below!

Fat Bear Week 2021: Before-and-After Pictures of the Contenders

Although this year’s winner has already been voted for (all hail Otis) there is always next year to pick out your bracket and vote for the bear that you think deserves the honours of being the Fat Bear Champion.

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.

Hungry Hyenas Help Human Health

Image Credit: flowcomm, CC BY 2.0, Image Cropped

Public health and economic benefits of spotted hyenas Crocuta crocuta in a peri-urban system (2021) Sonawane et al., Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.14024

The Crux

The natural world provides as with a laundry list of health services, from cleaning the water we drink to providing blueprints for cutting edge medicine. Yet on this list of ecosystem services, carnivores often get left by the wayside. One such carnivore is the spotted hyena, which can be found roaming the outskirts of many towns in eastern Africa. The hyenas are adept scavengers, and clear away massive amounts of discarded meat every year, potentially preventing the spread of carcass-borne diseases like anthrax and tuberculosis.

Yet as with many predators, hyenas have often been feared, whether as a result of their historical association with evil spirits or more recent unfavourable portrayals. In a world where carnivores like wolves, dingoes and bears are often feared and driven off, providing proof of the benefits they bring is crucial. So that’s what today’s researchers set out to do.

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The Ecology of The Lion King (With Lion Specialist Maria Gatta)

Image Credit: Wade Tregaskis, CC BY-NC 2.0, Image Cropped.

If there’s one film that I could perhaps credit for sparking my fascination with the natural world, the it’s The Land Before Time. BUT if we’re going with films that do not feature the most gangly Pachycephalosaurids you ever did see, then it has to be The Lion King. The sweeping landscapes, the (at times literal) fountains of species, the Shakespearian drama, the poor understanding of trophic cascades – it’s got it all.

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