The abundance of false killer whale, Pseudorca crassidens (Artiodactyla: Delphinidae) in coastal waters of Golfo Dulce and Osa Peninsula, Costa Rica

• Published in: Revista de Biología Tropical
• Main Authors: Sánchez Robledo, Erika, Oviedo Correa, Lenin Enrique, Herra-Miranda, David, Pacheco-Polanco, Juan Diego, Goodman, Sierra, Guzman, Hector
• Format: Article in Journal/Newspaper
• Language: English
• Published: Universidad de Costa Rica 2020
• Subjects: population size; capture-mark-recapture; demography; management-conservation; coastal-seascape; tamaño de la población; captura-marcaje-recaptura; demografía; manejo-conservación; paisaje costero; Pacific; Falsa; Drake Bay; Killer Whale; Orca
• Online Access: https://revistas.ucr.ac.cr/index.php/rbt/article/view/37196; https://doi.org/10.15517/rbt.v68i2.37196

Introduction: False killer whale (Pseudorca crassidens) is a tropical and subtropical social species that live in groups with individuals of mixed ages and sex classes. False killer whales have been documented since the late 1990s in Southwestern Costa Rica. Objective: To estimate the abundance of false killer whales in Osa Peninsula waters. Methods: Cetacean surveys off the Osa Peninsula Waters (OPW), Costa Rica, yielded opportunistic encounters with false killer whales in Drake Bay and Caño Island (2001-2015) and observations during formal surveys in Golfo Dulce (2005-2015). Photo-identification data was analyzed using capture-mark-recapture models in the study area, through an open population (POPAN) framework, considering the effect of time on the parameters apparent survival and capture probability, producing an abundance estimate for a superpopulation in the entire study area. Results: False killer whale abundance in OPW is characterized by a small population size of no more than 100 individuals, complemented by a very low probability of encounter and a contrasting high apparent survival. Conclusions: This population estimate should be taken as conservative, however, the small population size of less than 100 individuals should be considered vulnerable, in contrast to the increasing anthropogenic impacts in the coastal seascape. We argue the potential occurrence of population units along the coastal seascape of the Pacific littoral and oceanic island-associated units at Isla del Coco. Introducción: La falsa orca es una especie gregaria tropical y subtropical, que vive en grupos con individuos de diferentes clases de edad y sexo. La falsa orca ha sido documentada en el sur-oeste de Costa Rica desde finales de los 90s. Objetivo: Evaluar el uso de hábitat de la especie en términos de abundancia. Métodos: Observaciones en campo para cetáceos en aguas de la Península de Osa (APO), incluyen encuentros oportunísimos en Bahía de Drake y la Isla del Caño (2001-2015), así como observaciones directas de Pseudorca ...