Oldies but goodies: Study shows why elderly animals offer crucial scientific insights

A new study on ageing in the animal kingdom has highlighted how urgently Earth’s oldest and wisest creatures must be protected, with knowledge and environmental stability lost due to human intervention. 

The new study, led by Charles Darwin University’s (CDU) Research Institute for the Environment and Livelihoods (RIEL), explores the consequences of the loss of old, often large and wise animals in the wild and the value these individuals have to scientific knowledge, biodiversity and more. 

Humans are responsible for the decline of these animals. The review explains how in freshwater and ocean environments, the oldest age-classes of fish have been depleted in most populations, and extremely old corals are being harvested and are irreplaceable within human lifespans. 

On land, poaching, trophy hunting, predator hunting and recreational harvests are responsible for the loss of other types of old animals. On land and sea, old animal decline is also caused by habitat loss, disease, extreme climate events. 

Lead author Dr R. Keller Kopf, an ecologist and senior lecturer with CDU and RIEL, said older animals offer unique biological functions and ecological knowledge, and provide important services humans rely on.

“In addition to their intrinsic biodiversity value and slower rate of recovery in response to human activities, the loss of old animals ultimately threatens the long-term sustainability and stability of ecosystems on which humans depend,” Dr Kopf said. 

“They are especially important for ecosystem services such as fisheries whereby old individuals appear to provide the stability to populations, yet they are selectively harvested”

Dr Kopf said these older individuals offer insights into a variety of areas, including reproduction, behaviour, knowledge and social structures, and their roles in ecosystems. 

“Old individuals of long-lived species such as elephants, whales and humans accumulate knowledge over long time-periods, and - among many other benefits - this allows them to provide better care of their off-spring or grand-offspring,” Dr Kopf said. 

“In some of these species, especially humans, grandmothers increase the probability of grand offspring surviving and going on to reproduce. In fish and other cold-blooded animals, older individuals generally continue to grow throughout life, and this allows them to increase the number of offspring they produce.”

Dr Kopf said management strategies and policies would need a long-term approach, into years and decades, for the successful conservation of these animals. 

“A new method of conservation management and policy is required, which we refer to as ‘longevity conservation’,” Dr Kopf said. 

“The International Union for the Conservation of Nature Red List, and United Nations Convention on Biological Diversity must begin to recognize ‘longevity depletion’ a global threat to biodiversity and the sustainability of life on Earth. 

“Fisheries management agencies should develop policy and assessment approaches to recognise and prevent ‘longevity overfishing’ - it is currently not recognized as a type of overfishing but is a likely cause of fisheries collapse and increasing volatility.”

The study was conducted with an interdisciplinary team of researchers from the University of Exeter, Charles Sturt University, Macquarie University, the Amboseli Trust for Elephants in Kenya, University of Stirling, and Texas A&M University. 

Loss of Earth’s old, wise and large animals was published in the journal Science.