Hawaiian Monk Seals Endangered
Marine Pollution, Shark Predation and Starvation Are Threats
Nov 12, 2007
The Hawaiian monk seal (Monachus schauinslandi) faces multiple threats. Many juveniles are dying of starvation and others suffer from entanglement in marine debris. With shark predation on the rise, human development in Hawaii increasing and climate change reducing the traditional resting and breeding beaches, recovery efforts are focused on keeping the young animals alive and protecting their habitat.
One of two surviving species of monk seal, the Hawaiian may be headed for critically endangered status as its population is expected to drop below 1000 animals within the next couple of years. The other, the Mediterranean monk seal, has been listed as critically endangered since 1996.
Reasons for Loss of Juveniles
The biggest concern is that juvenile Hawaiian monk seals are not making it to adulthood. Many are starving but no one is sure why. It is only in the last few years that biologists learned that Hawaiian monk seals travel more than 100 miles and dive to 1500 feet to feed. It may be that as the younger animals are developing they are unable to go as far or dive as deep to find typical prey such as octopus, crustaceans and bottom fish.
The majority of the Hawaiian monk seal population lives within the newly created Northwest Hawaiian Islands National Monument. But despite being a marine protected area, bottomfishing permits will continue to be issued for up to five years. Critically, those recent feeding studies have also shown that Hawaiian monk seals are heavily dependent on two types of bottom fish. It is not known whether intensive human fishing has reduced the amount of prey that was once close enough for younger animals to find.
Young Hawaiian monk seals that do find enough food run other risks, including entanglement in marine debris. Nearly 500 tons of ocean trash has been removed from prime monk seal habitat in the Hawaiian Islands over the last 12 years. Tighter rules on gillnet fishing may also help reduce entanglement issues. Increased predation by Galapagos sharks, itself a species listed as Near Threatened, is another critical issue but the reasons for this increase are not well understood.
Climate Change and Human Disturbance
The one thing that is understood is that climate change has had an impact on traditional Hawaiian monk seal resting beaches. Rising water levels have reduced the size of some of those beaches to the point where there is discussion of shoring them up to provide more habitat for the seals within the marine protected area.
As Hawaiian monk seals attempt to return to the more populated islands, development is also causing problems. People and pets, especially dogs, disturb resting monk seals and have the potential to spread disease. Hawaiian monk seals haul out on beaches to rest between foraging bouts. If they are disturbed, they use valuable energy moving to a different site adding to their need for more food.
The Recovery Plan and Captive Care Project
In the recently released Hawaiian Monk Seal Recovery Plan in addition to habitat conservation, reducing fisheries impact and continuing population research and monitoring, a Captive Care and Release Project was set up to address the risks to juvenile Hawaiian monk seals. By keeping recently weaned seals penned at Midway Atoll, shark attacks can be prevented and debris kept away from the animals. Ensuring a food supply means pups will not starve.
When the seals in the Captive Care Project are in good condition they are released back to the wild, some with satellite transmitters which will add to the knowledge of juvenile behavior. This may shed some light onto the reasons for their high loss rate and ways to enhance their survival. It will certainly be an important part of the efforts to prevent the extinction of the Hawaiian Monk Seal.
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