As the world warms, living things are already trying to adapt to the changing environment, but new research suggests some species’ responses may lead them to even bigger problems.
One thing which is shifting as a result of the worsening climate crisis is the timing of major events such as reproduction. For example, in places which experience an earlier spring thaw, some flowers are also now blooming earlier.
This can then have a knock-on effect on insects and the birds which depend on the insects.
Or, timings can move the other way. A new study highlights the issues the rising global temperatures pose to African wild dogs, which over the last 30 years have rapidly adjusted their birthing dates later in the year by 22 days.
This adaptation allows the dogs to match the birth of new litters of pups to the coolest temperatures in winter, however, the cubs are then still in their critical post-birth “denning period” when temperatures begin to rise again, resulting in fewer pups surviving .
This example highlights the building dangers threatening an already endangered species.
African wild dogs are distantly related to wolves and raise young cooperatively in packs, but their behavioral changed may have led them to be caught in what is known as a “phenological trap”
In a phenological trap, a species changes the timing of a major life event in response to an environmental cue – but that shift ultimately backfires due to unprecedented environmental conditions like the climate crisis.
Lead author of the research, Briana Abrahms, a University of Washington assistant professor of biology, said: “It is an unfortunate ‘out of the frying pan, into the fire’ situation.”
“African wild dogs shifted birthing dates later in order to keep pace with optimal cool temperatures, but this led to hotter temperatures during the denning period once those pups were born, which ultimately lowered survival.”
The study provides evidence that species at high “trophic levels” in ecosystems, such as large predators, can be just as sensitive to the impacts of environmental breakdown as other species, something that scientists have been uncertain about.
Previous research has shown that long-term warming can trigger major shifts in species like plants and the “primary consumers” which feed on plants, such as birds and insects, but, until now, scientists had never documented a climate-driven phenological shift in a large mammalian carnivore.
The team based their research on more than three decades of data that they and collaborators collected on 60 packs of African wild dogs that live across more than 1,000 square-miles of northern Botswana.
The species breeds annually each winter and after birth, pups spend about three months with their mother at the den before beginning to travel and hunt with the pack.
Abrahms and her colleagues analyzed the dates that African wild dog mothers gave birth to their litters each year, which is how they determined that adults gradually delayed breeding by about one week per decade over 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 instance of a species delaying its life history, and at a rate twice as high as the average rate of change observed across animal species. ”, said Jeremy Cohen, a researcher at Yale University who was not involved in the study.
Such a large shift is likely due to the rapid pace of warming in the region, and because African wild dogs have evolved to breed within a narrow “thermal window,” Dr Abrahms said.
The team used long-term data on the wild dog populations to calculate how many pups survived the denning period each year.
They discovered a correlation between temperature patterns during the denning period and survival: Warmer denning periods led to fewer pups recruiting to packs at the end of winter, which they said indicated fewer pups survived the denning period.
Average daily maximum temperatures in the study period rose by about 1.6C (2.9F), over 30 years.
Over the same time frame, annual maximum temperatures spiked by 3.8C.
“We could only conduct this study because of the existence of this unique, long-term dataset for a large predator, which is really rare,” said Dr Abrahms.
“It shows the value for this kind of data in studying how climate change will impact ecosystems.”
The study area in northern Botswana is part of the largest continuous habitat for African wild dogs, which are threatened by habitat fragmentation and loss, disease and conflicts with people. The International Union for Conservation of Nature estimates that there are only about 1,400 mature adults left in the wild.
“Large predators play extraordinarily important roles in ecosystems, but we still have a lot to learn about the implications of climate change for these animals,” said Dr Abrahms.
“Big climate-driven shifts like the one we found may be more widespread in top predators than originally thought, so we hope our findings will spur new climate-change research on other predator populations around the planet.”
The research is published in the Proceedings of the National Academy of Sciences.