Where and how well mongooses are doing in Puerto Rico? A study of invasive mongoose in the island

Mongooses are an invasive species in Puerto Rico, causing the decline and extinction of local species such as birds, reptiles and amphibians. Diana is using molecular markers and stable isotopes to find out the spatial arrangement and connectivity of mongoose populations and their diet. This information will tell how mongooses are distributed in the landscape and its role as a widespread predator in the island. Ultimately, her study will help to focus efforts to control mongooses in the island.

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Small Indian mongoose (Herpestes auropunctatus). Photo by: J.N. Stuart at Flickr.com
Small Indian mongoose (Herpestes auropunctatus). Photo by: J.N. Stuart at Flickr.com
 Many animal and plant species found in areas where they did not occur in the past. These newcomers are known as invasive species. The consequences of having a new species could benefit the system by bringing new ecosystem services to the areas such as new pollinators for crops. Unfortunately in many cases the new species can have negative impacts at the community level by competing with local species and even displacing them. Diana is particularly interested in a species that has had mainly negative consequences for other species in places wherever it was introduced, the mongoose. Mongooses ( Herpestes auropunctatus) are native from India, and were introduced to Caribbean and Pacific islands at the end of the 20th century. These predators were brought into the area to control rats (another invasive) that were affecting sugarcane plantations. However, mongooses didn’t only eat rats it also local island species such as birds, amphibians and reptiles. Therefore this new species caused the decline and extinction of local species without eradicating the rat problem.

Local and federal agencies have tried to remove or reduce populations of mongoose from the islands but have failed because mongoose populations grew rapidly. Although they are omnivorous, mongooses keep predate especially local populations of ground nesting birds and marine tortoises among other species. However, there is little knowledge of the extent of the problem: how mongooses behave, its biology in the island, which species is eating the most or how the populations are related within and between islands. 

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Mongoose in live trap
Mongoose in the live trap will be checked for disease.

Diana is studying mongooses in Puerto Rico from multiple angles, to have a bigger picture of the problem. She wants to know where the mongooses populations are and how well connected the populations are to each other. She considers that populations that are connected are more difficult to manage, because removed mongooses will be easily replaced by individuals of adjacent connected populations. Diana will use molecular techniques to identify these connection patterns and how are natural or artificial barriers and other habitat features in the landscape limiting mongoose dispersal. She also wants to know what are preferred prey species of different populations of mongoose. By using stable isotopes, she will track the source of food of mongooses.

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Mongoose habitat probability map
Probability of mongoose occupying habitats in eastern Puerto Rico. Connectivity prediction was done using 34 mongooses trapped on the eastern part of the island via CIRCUITSCAPE using structural resistance. (Data on Cabo Rojo NWR was excluded)
Ultimately, Diana will have a sense of how the overall island community of wildlife species is assembled, having this predator already stablished from over a century. This information will be useful for wildlife managers and biologist who will know how the mongoose is distributed and prioritize areas to control the populations. With information about the trophic position and links of this predator, she will provide the base for research questions related to novel animal community assemblies and resilience after species introductions.