Distribution, habitat use and relative abundance of coastal tucuxi and bottlenose dolphins in the Gulf of Morrosquillo, Colombia
By Salomé Dussán-Duque, MSc

There are two species of coastal dolphins that share the habitats of the Gulf of Morrosquillo in Colombia: tucuxi and bottlenose. Coastal tucuxi have been designated in Colombia as a “vulnerable” species due to a moderate risk of extinction. Abundance appears to have declined by 30% or more in the last 10 years. In addition, the populations of bottlenose dolphins in Colombia are classified as “data deficient”. Clarification of the status of bottlenose dolphins in coastal Colombian areas is a priority for long-term conservation. The main threats for the Gulf of Morrosquillo populations of coastal dolphins are: changes in regional prey abundance and distribution, progressive loss of habitat, and direct catch for illegal marketing and display. The main goal of this project is to evaluate the distribution, habitat use and relative abundance of coastal tucuxi and bottlenose dolphins in the Gulf of Morrosquillo to develop guidelines for the management and long-term conservation of these species and their habitats.

From November 2002 through November 2005 we collected data for a total period of seventeen months, making this project the longest ongoing research on coastal dolphins in Colombia. We collected behavioral, geo-physical, environmental, photo-ID, acoustic, and carcass data. During 2005 we started recording the vocal behavior of tucuxi through a sister project with the University of Pavia, Italy and the IMR in Norway. The data are still being analyzed, using mainly ArcGis, capture-recapture techniques and the acoustic software Raven (University of Cornell). The results are being compared to previous studies of colleagues in Colombia and Brazil. Preliminary findings for both species include: 1) sightings per unit of survey effort are less frequent now than reported in 1994, 2) use of Cispatá Bay is significantly less than that reported in 1994 and 1998, 3) some individuals seem to be permanent residents of the area over the last 10 years (n = 3), 4) there is a strong tendency for site fidelity to the feeding grounds through the years, 5) the presence of specific individuals fluctuates through the seasons and 6) the vocal behavior of tucuxi in the area seems to be similar to that reported in study areas of Brazil, although it reached higher frequencies.

On the 30 July 2005, I traveled to the islands in the northern part of the Gulf, where a zoo has held two tucuxi dolphins under poor conditions for 10 years. On my visit I found another two tucuxi in a new pool that were captured toward the end of June in my study area. One of the individuals was recognizable and had been identified in the wild during October 2004. The health of the dolphins did not appear to be very good.

The category of “vulnerable” makes the capture and maintenance in captivity of this species in Colombia illegal. Permission for releasing of the dolphins was granted after a legal process that lasted for almost a month. On 26 August 2005, in a cooperative project between different organizations, we traveled to the islands to release the dolphins. The dolphin that was identified previously was not in the facility anymore, and the owners of the zoo did not provide clear information about its absence. We released the other tucuxi in one of the areas with a high number of sightings of this species. We are currently proceeding with obtaining permission from the government to release the two dolphins still remaining in the facility. We plan to work with the SDRP to radio-track and monitor the dolphins upon release.

Based on the preliminary results of this project, a designation of “Environmental Protected Area” in the Gulf of Morrosquillo was approved for both species this year. This is a major outcome for the project and the long-term conservation of both species and their habitats. The EPA will be part of a bigger management area for different species of fauna and flora. It will include the 33 National Parks of Colombia. We are currently working with different colleagues on developing management plans for each species. Our data on Gulf of Morrosquillo species and habitats are being compiled to be presented to the Colombian Environmental Ministry in support for the creation of a National Park. The year 2006 promises to be a very important and a busy year for our research. We would like to thank the support of the Chicago Zoological Society, Corporación Autónoma Regional de los Valles del Sinú y del San Jorge, Colombia and Conservación Internacional, Colombia.