GRADUATE STUDENTS

Hana López

by Suzanna Engman

Hana López, graduate student at the University of Puerto Rico, Río Piedras and full time biologist employed by the Department of Natural and Environmental Resources (DNER), studies exotic, or introduced, goats on Mona Island. The goats were brought some 500 years ago by Spaniards and let loose to reproduce and provide food for travelers to the Caribbean. Currently, the goat population on Mona Island is controlled by hunters, who are permitted to hunt feral goats and pigs during the hunting season from December to March. Population studies have estimated that between 1500 and 3000 goats live on the island. Although they keep a low profile around humans, their impact on ecosystems is profound. The goat (Capra hircus) is cited as one of the “100 of the World’s Worst Invasive Alien Species,” on a list compiled by the World Conservation Union (ICUN) . They compete for shelter, water and food resources with native species. Goats eat almost any vegetation, facilitating the establishment of invasive plants. This, coupled with their behavior—males pawing the ground and the herd’s hoofs—contribute to soil erosion.

For Lopez’ study, some of the animals are shot with a transmitter dart that contains a tranquilizer. The transmitter signal in the dart allows researchers to locate and track animals that are difficult to capture for study. While a goat is down, López collects other data, for example the goat’s age, which can be estimated by observing its teeth. Her study will determine goat movement on the island using GPS-collar transmitters and the relationship of the space each animal uses with respect to the wet and dry seasons and hunting activity. She will also estimate the sex and age ratio of the goat population by comparing their presence in three habitats: plateau, depression, and lowland coastal forests. This information will be useful in determining an introduced feral goat population management policy on the island.

Other invasive mammals on Mona Island include the domestic cat, pigs, and ship rats. According to the IUCN, invasive species are second only to habitat loss in causing endangerment and extinction of native species. López’ DNER work centers on exotic species. At present, she is eradicating feral cats on Mona Island as a conservation approach. The estimated 200 cats prey on the island’s endangered Mona Island iguanas and boas, as well as other endemic and native fauna. López notes that total eradication may not be the best route to take to restore balance in the island’s ecosystems because cats may play an important role in controlling ship rat and mice populations. “If all the cats were eradicated, the unchecked rat population might cause even worse problems. Population management rather than total eradication might be a better strategy.”

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