Natural Causes:
* Predation: Orcas (killer whales) are the primary predators of adult harbor seals, while sharks, sea lions, and large fish can prey on pups and juveniles.
* Starvation: Limited food availability during harsh winters or periods of low fish abundance can lead to starvation, particularly for pups and young seals.
* Disease: Viral and bacterial infections, including distemper, can cause significant mortality, especially in pups.
* Parasites: Internal and external parasites can weaken seals, making them more susceptible to disease and predation.
* Severe Weather: Storms and cold snaps can cause hypothermia and drowning, especially for young seals.
* Competition: Competition for food and breeding territories with other seals can lead to injuries and even death.
Human-Made Causes:
* Bycatch: Harbor seals are frequently caught accidentally in fishing nets, leading to drowning or injury.
* Pollution: Oil spills, chemical pollution, and plastic ingestion can cause death or long-term health problems.
* Habitat Degradation: Loss and degradation of coastal habitats, such as beaches and haul-out sites, can reduce breeding success and overall survival.
* Climate Change: Changes in ocean temperatures and currents can impact food availability and lead to increased competition and disease outbreaks.
* Boat Collisions: Collisions with boats can cause serious injuries and death.
* Harassment: Disturbance by humans can disrupt breeding and nursing activities, leading to stress and even abandonment of pups.
It is important to note that the relative importance of these factors can vary depending on the specific location and time period.
Conservation Efforts:
Efforts to protect harbor seals include:
* Reducing bycatch: Using fishing gear modifications and stricter regulations to minimize accidental catches.
* Controlling pollution: Reducing pollution from industrial sources and improving waste management practices.
* Protecting habitat: Creating marine protected areas and restoring damaged coastal ecosystems.
* Managing human activities: Regulating boat traffic, restricting access to sensitive areas, and promoting responsible tourism.
By addressing these threats, we can help ensure the survival of harbor seals and other marine wildlife for generations to come.