been observed. Reduced prey abundance can lead to starvation, with one cause being reduction in habitat associated with environmental change. Habitat is shrinking due to erosion in the Northwest Hawaiian Islands, reducing the size of islands/beaches. Lobsters, the seals' preferred food other than fish, have been overfished. Competition from other predators such as sharks, jacks, and barracudas leaves little for developing pups. The creation of Papahānaumokuākea Marine National Monument which encloses these islands may expand food supplies. Mobbing is a practice among the seals that involves multiple males attacking one female in mating attempts. Mobbing is responsible for many deaths, especially to females. Mobbing leaves the targeted individual with wounds that increase vulnerability to sepsis, killing the victim via infection. Smaller populations were more likely to experience mobbing as a result of the higher male/female ratio and male aggression. Unbalanced sex-ratios were more likely to occur in slow-growing populations. Postmortem examinations of some seal carcasses revealed gastric ulcerations caused by parasites. Some of the infectious diseases that pose a threat to the Hawaiian monk seal populations include distemper viruses, West Nile Virus, Leptospira spp., and Toxoplasma gondii. Protozoal-related mortality, specifically due to toxoplasmosis, are becoming a great threat to the recovery of the endangered Hawaiian monk seal and other native Hawaiian marine life. Anthropogenic impacts In the nineteenth century, large numbers of seals were killed by whalers and sealers for meat, oil and skin. U.S. military forces hunted them during World War II, while occupying Laysan Island and Midway. The Hawaiian monk seal has the lowest level of genetic variability among the 18 pinniped species. This low genetic variability was allegedly due to a population bottleneck caused by intense hunting in the 19th century. This limited genetic variability reduces the species ability to adapt to environmental pressures and limits natural selection, thus increasing their risk of extinction. Given the monk seal's small population, the effects of disease could be disastrous. Monk seals can be affected by the toxoplasmosis pathogen in cat feces that enters the ocean in polluted runoff and wastewater, a new phenomenon. Since 2001, toxoplasmosis has killed at least eleven seals. Other human-introduced pathogens, including leptospirosis, have infected monk seals. Human disturbances have had immense effects on the populations of the Hawaiian monk seal. Monk seals tend to avoid beaches where they are disturbed; after continual disturbance the seal may completely abandon the beach, thus reducing its habitat