A new study has found that in many animals societies, older individuals are vital participants in the survival of their species. That’s why wildlife conservation needs to take older animals into account.
Keller Kopf, lead author and ecologist at Charles Darwin University, Australia, told Mongabay that he wanted to counter the idea that “getting older is always horrible.”
While aging is often linked to declining health and function, there is growing evidence that older animals offer many benefits, Kopf said via smartphone. However, he added, most of this research had been done for extraordinary animal agencies in isolation, so the new study aimed to bring those findings together.
Older Animals Offer Wisdom And Balance
Older individuals, the study found, provide greater balance to their populations and ecosystems. For example, some older fish mothers lay more eggs in better habitats than their younger counterparts, and some older bird fathers provide better food and care for their chicks. Certain deep-sea corals having a life span of hundreds of years are critical to the survival of several marine animals, providing food and shelter. These are “basically irreplaceable during a human lifetime,” Kopf said.
The study also highlighted how older animals bring valuable “knowledge,” or experience accumulated over their lives, to their societies. Animals such as whales, elephants, and some migratory birds and fish, for example, rely on older individuals to guide them in finding food and better breeding grounds. In contrast, in species with strong social systems, such as sea lions, the death of older leaders can destabilize the shape of the population, Kopf said.
The study is “comprehensive and compelling,” Tim Coulson, a professor of zoology at the University of Oxford, UK, who was involved in the study, told Mongabay. It shows that our preoccupation with catching large, old fish, or the tallest, oldest trees, is misdirected, he added. The authors support that commercial management of species, particularly in fisheries, should prioritize the retention of older specimens.
“It’s a critical issue for reflection,” said Lewis Barnett, a fish biologist at NOAA Fisheries, USA, who was not involved in the study. He agreed with the authors that in policy responses to protect older fish, recreational fisheries should increasingly be taken into account, where the harvest may be more selective, or individuals might survive the risk of live release.
In industrial fisheries, however, “the most effective tools may be spatial control and non-use of harvest zones, changing tools, and reducing standard catch quotas,” he added.
The authors also recommend that the IUCN red list include “age class” in its species reputation checks; this is no longer the practice. This is like an old-growth forest, Kopf said: “You can take out all the big trees, and that’s just going to give you a large population of small trees. That does not mean, however, that it is going to bode well for that population or the species.”
Coulson said that while an “outstanding proof of concept” — including the reputation of older individuals in IUCN checks — is an “unrealistic expectation,” given the data needed to robustly capture the impact of such individuals on fluctuating populations.