Manatees are large, herbivorous marine mammals. Their lifespan varies significantly between wild populations and those under human care. Understanding the factors influencing their longevity provides insight into their biology and the challenges they face. This article explores manatee lifespan in both wild and captive environments.
Manatee Lifespan Overview
Manatees living in the wild generally have the potential to live for 50 to 60 years. Despite this potential, many wild manatees do not reach their full lifespan, with a significant number not surviving beyond ten years. In contrast, manatees in captive environments often live longer, frequently exceeding 65 years.
The extended lifespan in captivity stems from a controlled and protected environment. Captive manatees benefit from consistent food availability, absence of natural predators, and readily accessible veterinary care. These conditions mitigate many of the threats that limit longevity in wild populations, allowing manatees to live closer to their biological maximum age.
Factors Shaping Manatee Longevity
Manatee longevity is influenced by natural occurrences and human activities. Natural factors include diseases, parasites, and cold stress; prolonged exposure to water temperatures below 68°F (20°C) can be fatal. Loss of access to warm water refuges exacerbates this threat. While adult manatees have few natural predators, sharks, alligators, and crocodiles may prey on calves. Starvation and malnutrition also occur, especially when seagrass beds decline due to environmental degradation.
Human activities pose the most substantial threat to wild manatee longevity. Boat collisions are a leading cause of mortality, often from propeller strikes or vessel hulls; 96% of adult Florida manatees bear boat strike scars. Habitat loss and degradation, driven by coastal development and pollution, destroy essential seagrass beds and safe havens. Entanglement in fishing gear can lead to severe infections, amputations, or death. Other dangers include harmful algal blooms (red tide), flood gates, canal locks, and ingesting debris or pollution.
Assessing Manatee Age and Record Holders
Scientists determine a manatee’s age primarily by examining its ear bones, specifically the periotic bones. These bones develop annual growth layer groups (GLGs), similar to the rings found in tree trunks. Researchers meticulously count these layers to estimate the manatee’s age after death. Unlike some other marine mammals, manatee age cannot be determined by their teeth due to their continuous replacement.
Accurately aging living wild manatees presents challenges, as the ear bone examination requires access to deceased individuals. For living manatees, age is often approximated based on their size, developmental stage (calf, subadult, or adult), or known birth dates, particularly for those in managed care. Bone resorption in older manatees can sometimes obscure the growth layers, making precise age estimation more difficult.
Snooty, a male West Indian manatee born in captivity, is a remarkable example of longevity. He lived an impressive 69 years (July 21, 1948 – July 23, 2017) at the South Florida Museum’s Parker Manatee Aquarium. Snooty held the record as the oldest manatee in captivity, and possibly the world. His exceptionally long life demonstrated the potential lifespan of manatees with optimal care and protection.