Top predators could ‘trap themselves’ trying to adapt to climate change, study finds

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June 27, 2022

African wild dog puppies.Vial Bobby-Jo

As climate change alters environments around the world, scientists have found that in response, many species are altering the timing of major life events, such as reproduction. With an earlier spring thaw, for example, some flowers bloom earlier. But scientists don’t know whether these significant changes in life history will ultimately help a species survive or lead to bigger problems.

A study published the week of June 27 in the Proceedings of the National Academy of Sciences shows for the first time that a species of large carnivore has made a major change to its life history in response to a changing climate – and perhaps worse for this.

African wild dog puppies.Vial Bobby-Jo

A team led by researchers from the University of Washington, in collaboration with Botswana Predator Conservation, a local NGO, analyzed field observations and demographic data from 1989 to 2020 for wild dog populations — wild dog pictus. They found that, over a 30-year period, the animals shifted their average birth dates by 22 days later, an adaptation that allowed them to match the birth of new litters with the cooler temperatures at the start of Winter. But as a result of this significant change, fewer young have survived their most vulnerable period as temperatures during their critical post-natal “calving period” have risen over the same period, threatening the population of this species. already endangered.

This study shows that wild dogs, which are distantly related to wolves and raise their young in groups, may be caught in a “phenological trap,” according to lead author Briana Abrahms, an assistant professor of biology at UW and a researcher at Center for Sentinels of the Ecosystem. In a phenological trap, a species changes the timing of a major life event in response to an environmental cue – but this change proves maladaptive due to unprecedented environmental conditions like climate change.

“It’s an unfortunate ‘out of the frying pan, into the fire’ situation,” Abrahms said. “African wild dogs shifted birth dates later in order to keep pace with optimal cool temperatures, but this led to warmer temperatures during the whelping period once these pups were born, which ultimately reduces survival.

An African wild dog mother and puppy.Vial Bobby-Jo

The study demonstrates that species at high “trophic levels” in ecosystems – such as top predators – may be just as sensitive to climate change as other species, which scientists were unsure of. Other research has shown that long-term warming can trigger phenological changes, or shifts in the timing of major life events, in “primary producer” species like plants and “primary consumers” that feed of plants, including many birds and insects. But, until now, scientists had never documented a climate-related phenological change in a large carnivorous mammal. Abrahms and his colleagues show that top predators can indeed exhibit strong responses to long-term climate change, even if the predators are “further back” in the food chain.

For this study, the team analyzed more than three decades of data that they and their collaborators collected on 60 packs of wild dogs that live in an area of ​​more than 1,000 square miles in northern Botswana. This species breeds annually every winter. After birth, the pups spend about 3 months with their mother at the den before they begin to travel and hunt with the pack.

An African wild dog mother and her puppies.Krystyna Golabek

Abrahms and his colleagues analyzed the dates when African wild dog mothers gave birth to their litters each year, which is how they determined that adults gradually delayed reproduction by about a week per decade over the course of a decade. the 30-year study period.

“Although most animal species are advancing their life history events earlier in the year with climate change, this finding represents a rare case of a species delaying its life history, and at twice the rate. higher than the average rate of change seen in animal species,” said Jeremy Cohen, a researcher at Yale University and the Center for Biodiversity and Global Change, who was not involved in the study.

Such a dramatic change is likely due to the rapid rate of warming in the region and the fact that wild dogs have evolved to breed within a narrow “thermal window,” according to Abrahms.

The team used long-term demographic data to calculate how many pups survived the calving period each year. They found a correlation between temperatures during the calving period and survival: warmer calving periods resulted in less recruitment of pups to packs in late winter, indicating that fewer pups survived the calving period.

Average daily high temperatures over the study period have increased by about 1.6 degrees Celsius, or 2.9 degrees Fahrenheit, over 30 years. During the same period, annual maximum temperatures rose by 3.8 degrees Celsius, or just over 6 degrees Fahrenheit.

African wild dog puppies.Peter Blinson

The team could not have reached its unexpected conclusions without decades of detailed field observations conducted by Botswana Predator Conservation, Abrahms said.

“We were only able to conduct this study because of the existence of this unique long-term data set for a large predator, which is really rare,” Abrahms said. “This shows the value of this type of data for studying the impact of climate change on ecosystems.”

The study area in northern Botswana is part of the largest continuous habitat for wild dogs, which are threatened by habitat fragmentation and loss, disease, and conflict with humans. The International Union for Conservation of Nature estimates that there are only about 1,400 mature adults left in the wild.

“Top predators play an extraordinarily important role in ecosystems, but we still have a lot to learn about the implications of climate change for these animals,” Abrahms said. “Big climate-related changes like the one we found may be more widespread among top predators than originally thought, so we hope our findings will spur further research on climate change in other places. predator populations around the planet.”

A pack of wild dogs in Kruger National Park, South Africa.Bart Swanson

The study’s co-authors are Kasim Rafiq, postdoctoral researcher in biology at UW; Neil Jordan of the University of New South Wales; and JW McNutt with Botswana Predator Conservation. The research was funded by numerous public and private donors over the thirty-year study period.

For more information, contact Abrahms at [email protected]

Tag(s): Briana Abrahms • Center for Ecosystem Sentinels • climate change • conservation • Department of Biology • ecology

Teresa H. Sadler