Image Credit: Kevin Pluck, CC BY 2.0, Image Cropped
Brain expansion in early hominins predicts carnivore extinctions in East Africa (2020) Faurby et al, Ecology Letters, https://doi.org/10.1111/ele.13451
We’ve covered humans and their harmful effects many times here on Ecology for the Masses (see my recent breakdown from last month). Despite all of the colorful examples of our current effects on the wildlife of our planet, a significant amount of research has implicated Homo sapiens as the driver of the extinction of some of the megafauna of the prehistoric world, events that happens millions of years ago. Another possibility is that we as organisms (hominins, not Homo sapiens specifically) have been impacting other species for a very, very long time.
Today, East Africa is home to the most diverse group of large carnivores on the planet (though it is still less diverse than what was once seen in North America and Eurasia). Millions of years ago East Africa had an even more diverse assemblage of large carnivores, including bears, dogs, giant otters, and saber-toothed cats. The change in climate since that time may have caused the decline in large carnivore diversity, but another explanation is the rise of early hominins (our ancestors). Using fossil data, the authors of today’s paper wanted to figure out if it was indeed early hominins that drove many large carnivores extinct.
Image Credit: Kevin Gill, CC BY 2.0, Image Cropped
No consistent effects of humans on animal genetic diversity worldwide (2020) Millette et al, Ecology Letters, https://doi.org/10.1111/ele.13394
As a species, we humans have had enormous negative effects on the planet, and we have talked about many of these issues and how they relate to ecology on many separate occasions here on Ecology for the Masses (see here, here, and here). A key implication of these human-induced changes to our planet are that many organisms are threatened with extinction, which can be bad for us as well (looking at you insect apocalypse).
Having said all of that, a lot of the work that has been done in this area has focused on specific groups (like the charismatic koala). By doing so, we run the risk of not understanding the global pattern but instead draw conclusions based off of local patterns. While we sometimes must make these kind of generalizations, this is not always a good idea. For example, we cannot look at the health of animal populations in New York City and make statements about the entirety of all of the animal populations in North America. To get around that issue, today’s authors investigated, on a global scale, if humans were having a global impact on animal genetic diversity.
Image Credit: Andrew DuBois, CC BY-NC 2.0, Image Cropped
Behavioural fever reduces ranaviral infection in toads (2019) Sauer et al, Functional Ecology, https://doi.org/10.1111/1365-2435.13427
Being infected with a pathogen such as a bacteria or virus can be bad for whatever organism is unfortunate enough to suffer the infection, and sometimes it’s bad enough to kill the host. Because of that, there is a strong pressure to engage in behaviors that reduce the chances of becoming infected in the first place. While these behaviors can be inherited and evolve over time, others take place within the lifetime of the infected individual itself, making it a ‘plastic’ response (see the “Did You Know” from our previous breakdown for the difference between plasticity and evolution).
One plastic response is that of a behavioral fever. In organisms that cannot regulate their own body temperature, like reptiles and amphibians, this behavior involves moving from an area with low temperature to one with a higher temperature, ideally limiting the damage that a pathogen can do or even killing it outright. Because this behavioral fever is so dependent on temperature, it is important to know how climate change may impact emerging infectious disease.
Image Credit: Swallowtail Grass Seeds, Public Domain Mark 1.0, Image Cropped
There has been a lot of recent (and well deserved) press surrounding the bush fires in Australia. Because of these fires countless animal and plant life has been lost, and the most visible example of that are the koalas. You probably saw the video of a woman running into a burning area to save a koala from the fire*. Unfortunately, most of the koalas didn’t have people around to save them and over 1,000 are estimated to have died. Because of this a group has claimed that koalas are now “functionally extinct”, and the press has run with this claim. While it is unfortunate that this misinformation spread so quickly and so widely, the good news is that koalas are in fact NOT functionally extinct. Great! But what does being “functionally extinct” mean?
Mandt’s Black Guillemont (Image Credit: Óskar Elías Sigurðsson, CC-BY 2.0, Image Cropped)
Phenotypic plasticity or evolutionary change? An examination of the phenological response of an arctic seabird to climate change (2019) Sauve et al., Functional Ecology, https://doi.org/10.1111/1365-2435.13406
If you’re here on Ecology for the Masses, then you know that climate change is not only real but is causing all kinds of problems for organisms the world over. One of the things that climate change is doing is altering seasonality, the time of year in which a given season will take place. For example, where I live in the US, it is normally cold at this time of year, but as I write this it is 60F/16C, much warmer than it should be despite it almost being winter. These changes can affect when organisms start their seasonal breeding, but how these breeding events change is not always the same.
Some changes are due to evolution, or the change in a population’s gene frequencies over time. As mutations and selection take place, a given population may have some traits or behaviors selected for over others. Another way that these changes can happen is via plasticity, which is a change induced by the environment, but without changing the gene frequencies (See Did You Know? for more information). The authors of today’s paper wanted to know if the change in breeding dates of a colony of seabirds (Mandt’s black guillemont, Cepphus grylle mandtii) was due to evolution or plasticity.
Male echidna must stay on the move to find females before other males do (Image Credit: JKMelville, CC BY-SA 3.0, Image Cropped)
Energetics meets sexual conflict: The phenology of hibernation in Tasmanian echidnas (2019) Nicol et al., Functional Ecology, https://doi.org/10.1111/1365-2435.13447
Seasonality (i.e. the change in season throughout the course of the year) has huge impacts on the lives of animals that live in temperate habitats. The change in season is associated with changes in food availability, and as such some animals hibernate through the tough winter months and wait until the food and warmer weather comes back. Another aspect of an animal’s life impacted by seasonality is the breeding season, as animals living in temperate habitats must time their breeding around the winter months, while animals in tropical habitats can breed year-round.
Within a single species the timing of hibernation may be affected by the different energetic and reproductive needs of the different sexes. Females may start hibernating later than males because they have to store more energy for their pregnancy and lactation, while males may emerge from hibernation earlier than females to establish territories and increase their chance of mating. Tasmanian echidnas (Tachyglossus aculeatus) exhibit markedly different hibernation patterns among the sexes, and the authors of today’s study wanted to know if these differences are due to where they live or whether they are inherent to the species itself.
For small animals like the mouse, predators are a constant concern (Image Credit: Jess, CC BY-NC 2.0)
Maximising survival by shifting the daily timing of activity (2019) van der Vinne et al., Ecology Letters, https://doi.org/10.1111/ele.13404
All animals need to eat food to survive and maintain their energy balance, but unlike us they can’t just order a pizza and have the food brought to them. They must always forage for food themselves, and every time that they do they expose themselves to predators. Small mammals like mice balance this trade-off by foraging for food at night, when their risk of predation is lowest.
One interesting strategy that mice can employ is to switch their foraging from the nighttime to the day, if they cannot get enough resources during the night or if their nighttime predation risk increases. The authors of today’s paper wanted to develop a model to predict under what conditions these temporal switches would occur, a model which they then tested with mice in the field.