In many animal societies, elderly individuals are critical contributors to their species\u2019 survival, a new study has found. That\u2019s why wildlife conservation must account for older animals, researchers say.<\/p>\n
Keller Kopf, lead author and ecologist at Charles Darwin University, Australia, told Mongabay he wanted to counter the idea that \u201cgetting old is always a bad thing.\u201d<\/p>\n
While aging is often linked to declining health and function, there\u2019s mounting evidence that older animals offer many benefits, Kopf said by phone. However, most such studies have been conducted for different animal groups in isolation, he added, so the new review aimed to bring those findings together.<\/p>\n
Older individuals, the review found, provide greater stability to their populations and ecosystems. For instance, some older fish mothers lay more eggs in better habitat than their younger counterparts, and some older bird parents provide better food and care for their chicks. Certain deep-sea corals that live for thousands of years provide critical food and shelter for a wide range of marine animals. These are \u201cessentially irreplaceable within human lifespans,\u201d Kopf said.<\/p>\n
The review also highlighted how older animals contribute valuable \u201cwisdom\u201d or knowledge accumulated over their lifetime to their societies. Animals like whales, elephants and some migratory birds and fish, for example, rely on older individuals for guidance to find food and better breeding areas. Conversely, in species with strong social structures, like wolves, the death of older leaders can destabilize the pack structure, Kopf said.<\/p>\n
The review is \u201ccomprehensive and compelling,\u201d Tim Coulson, a zoology professor at the University of Oxford, U.K., not involved in the study, told Mongabay. It also shows that \u201cour fixation on harvesting large, elderly fish, or the tallest, oldest trees is seriously misguided,\u201d he added.<\/p>\n
The authors recommend that commercial management of species, particularly in fisheries, should prioritize preserving older individuals.<\/p>\n
This is \u201cimportant food for thought,\u201d said Lewis Barnett, a fish biologist at NOAA Fisheries, U.S., not involved in the study. He agreed with the authors that policy solutions around protecting older fish could work with recreational fishing where \u201charvesting can be more selective, or where individuals can be released alive with a high chance of survival.\u201d<\/p>\n
However, in commercial fisheries, \u201cthe more practical tools may be spatial management with no-take areas, gear modification, and reduced harvest rates overall,\u201d he added.<\/p>\n
The authors also recommend that the IUCN Red List incorporate \u201cage class\u201d in its assessments of species\u2019 status, currently not the practice. This is akin to an old-growth forest, Kopf said: \u201cYou can chop down all of the big trees and still have a huge number of really young trees. But it doesn\u2019t mean that the population or that species is necessarily in good shape.\u201d<\/p>\n
Coulson said that while a \u201cnice thought experiment,\u201d including the status of older individuals into IUCN assessments is an \u201cunrealistic expectation,\u201d considering the information needed to robustly capture the impact of such individuals in fluctuating populations.<\/p>\n