Tag Archives: predator

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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Hippocracy

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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What’s In A Wolf Scat? New DNA-Based Method To Detect Prey From Carnivore Scats

This is a guest post by Cecilia di Bernardi.

Image Credit: Rick Heeres, CC BY 2.0, Image Cropped

Multiple species-specific molecular markers using nanofluidic array as a tool to detect prey DNA from carnivore scats (2021) Di Bernardi et al., Ecology & Evolution. https://doi.org/10.1002/ece3.7918

The Crux

Studying carnivore diet can be a crucial tool to inform both management and conservation of predators and their prey. If we’re going to ensure a carnivore’s survival, we need to know which species it relies on for food, and in what quantities.

Digging into an animal’s stomach isn’t the nicest way to get the crucial data we’re looking for, so non-invasive sampling of scats (that’s science for poop) has for been a more ideal approach to collecting valuable information on the occurrence, genetics, and diet of animals, especially when dealing with elusive and threatened species. Nowadays, DNA-based analyses of scats are allowing researchers to get more and more high-resolution data on predators’ food habits.

What We Did

We developed a DNA-based method to detect prey from wolf scats, taking advantage of the huge leaps the DNA analysis has been through in recent years. We also made use of nanotechnology (specifically Nanofluidic array technology fromFluidigm Inc.), which has been useful for detecting pathogen species in ticks, or traces of herbivores on browsed twigs, but has never applied to detect prey from predator scats!

Starting from the big bank of DNA sequences available online (GenBank, NCBI), we looked at specific areas of the genome, (the mitochondrial genome), in order to tell apart the different target prey species present in the wolf scat. We developed species-specific molecular markers (see Did You Know?) and tested them with reference tissue samples, kindly provided by the Swedish Museum of Natural History. After the protocol development and optimization, we ended up with a set of 80 markers for our 18 target species. We then applied the newly developed molecular method on a pilot sample of wolf scats collected in the field.

Did You Know: Molecular Markers

Since any species’ genome is an incredibly long sequence, scientists have developed more efficient ways of defining what DNA belongs to which species. The motivation is simple – if you’re trying to tell whether a genome belongs to a human or to a chimpanzee, you don’t want to be looking through the 99% of DNA we have in common, you want to go straight to that 1%. That’s why scientists develop ‘markers’. It helps them narrow down their search and identify species much more quickly.

What We Found

The molecular markers we developed did their job well, correctly detecting the 18 prey species, showing an overall good distinction between the tissue samples of the target and non-target species. In other words, this means that a tissue sample taken from a moose was detected by the moose markers but not by the reindeer markers, which is the sign of a successful marker!

When applied to the pilot of wolf scats collected in the wild, the method detected a total of 16 species, comprising wild ungulates (moose, roe deer, red deer, fallow deer, wild boar), domestic and semi-domestic animals (reindeer, cattle, sheep), small prey species (European badger, European hare, mountain hare, Western capercaillie, black grouse), and other carnivores (Eurasian lynx, wolverine, red fox).

Just because fox DNA turns up in a wolf scat, it doesn’t mean that a wolf has eaten a fox – it could simply mean tha a fox has urinated on the scat! (Image Credit: Joanne Redwood, CC0 1.0)

Problems?

While the method detects the target species as we’d like, it cannot distinguish whether predation, scavenging, or territorial marking has occurred. Detection of fox DNA in wolf scats can mean a wolf predating on a fox, a wolf scavenging on a fox, but also a fox marking with its urine on a wolf scat! To partly disentangle this aspect, we are investigating the contribution of scavenging to wolves diet in Scandinavia, with data from GPS-collared wolves.

So What?

This molecular method, with its high-resolution prey detection, can help better understanding under what circumstances wolves eat certain prey and how that can affect ungulate populations, serving as a valuable complement to the current GPS technology used to investigate wolf predation. Wolf natural expansion is an ongoing and controversial phenomena in the Northern hemisphere, and any technique that tells us more about their impact is a welcome addition to our knowledge base.


Cecilia Di Bernardi is an ecologist who is currently investigating wolf predation ecology within her PhD at the University of Rome La Sapienza in collaboration with SLU Swedish University of Agricultural Sciences. You can follow her on Twitter @c_dibernardi.

Not Giving Into the (Selection) Pressure

A common measure of prey immune function is not constrained by the cascading effects of predators (2021) Hasik et al., Evolutionary Ecology. https://doi.org/10.1007/s10682-021-10124-x

Image Credit: Adam Hasik, Image Cropped

The Crux

The immune function is a critical component of an organism’s ability to defend itself from parasites and disease. Without it, we would be in much worse shape when we got sick. Despite this usefulness, the immune function is costly to use as organisms have to consume enough food to have the energy needed to mount an immune response. This is easier said than done, however, and there are often many factors that come into play when it comes to acquiring energy.

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