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Elders in the Animal Kingdom
Context:
A 2023 review published in Science on November 21 highlighted the detrimental effects of human-caused disturbances on the loss of older individuals within species.
“Old” Defined Differently Across Species
- The concept of “old” varies: a three-year-old mouse might be considered old, while a 30-year-old elephant is relatively young.
- The importance of older individuals is tied to species characteristics such as social behaviour, parental care, and migration.
Research Findings:
- A study analysed over 9,800 peer-reviewed papers on the roles of elderly individuals, highlighting benefits such as knowledge transmission, assisting parental care, and coping with extreme weather.
- The study focused on long-lived mammals, birds, and cold-blooded animals (fish and reptiles), due to their more significant roles in social and ecological functions.
Role of Older Animals in the Wild:
- Older animals, like elephant matriarchs and shark grandmothers, hold valuable knowledge accumulated over their lifetimes, guiding their families through challenges.
- Older individuals stabilise social hierarchies, act as repositories of information, and provide guidance during tough times, benefiting their species.
- Elders are vital for navigating migration routes, helping with parental care, and preserving cultural knowledge.
Impact of Human Activities:
- Deforestation: Logging and land conversion for agriculture or urbanisation destroy the habitats of ancient trees and countless other species that depend on them.
- Pollution: Oceans and rivers are contaminated with plastics and chemicals, affecting marine creatures that have remained unchanged for millennia.
- Climate Change: Rising temperatures and altered weather patterns disrupt the delicate balance of ecosystems, pushing elder species to adapt rapidly or face extinction.
- Overexploitation: Unsustainable fishing, hunting, and harvesting practices deplete populations of long-lived species faster than they can reproduce.
Case Studies:
- Elephants: Young elephants rely heavily on the matriarch, the oldest female, for guidance.
- A 2011 study found that herds led by matriarchs more than 60 years old responded more effectively to threats.
- “If older individuals are removed from the wild, by capture or unnatural death, younger ones struggle to survive without their knowledge.
- A 2011 study found that herds led by matriarchs more than 60 years old responded more effectively to threats.
- Orcas: Older female orcas undergo menopause, contributing to the survival of their species by helping care for grandchildren, protecting them from predators, and guiding them to feeding grounds (known as the “grandmother hypothesis”).
Longevity Conservation:
- A new conservation paradigm called “longevity conservation” stresses the need to protect older members of species, especially those with complex social structures and cultural knowledge.
- Protecting older individuals, especially in long-lived species, is crucial not just for individual survival but also for the survival of the species as a whole, particularly in the face of climate change and human disturbances.
Challenges:
- Fisheries Management: In multi-species fisheries, such as in India, it is difficult to protect older, larger individuals while continuing to harvest other species.
- Different species age differently and have varying life histories, which makes targeted conservation strategies complex.
- Global Policy Challenges: The International Union for Conservation of Nature (IUCN) currently does not recognise the loss of older individuals as a criterion for listing threatened species despite its significant ecological importance.
