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Occurrence and distribution of false killer whales (Pseudorca crassidens) in Central America

Authors:
  • Centro de Investigacion de Cetaceos Costa Rica CEIC

Abstract

False Killer whales are listed as nearthreatened on IUCN red list, Lack of knowledgecon distribution and occurrence along the Pacific coast of Central America,
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PERSPECTIVE
Complete study with environmental
data to understand group size
difference between site
Complete photo-identification method
with genetic analysis to enhance our
understanding of population distribution
in Central America
Expand area of study to northern and
southern country to get movement
pattern of individuals.
False killer whales occur in three Central
American countries. Resighting between
Costa Rica and Panama but none with
Nicaragua. Indicates potential distinct
populations between Nicaragua and
southern Countries (Nicoya Ecoregion).
BACKGROUND
False Killer whales are listed as near
threatened on IUCN red list, Lack of knowledge
on distribution and occurrence along the
Pacific coast of Central America,
OBJECTIVE
Understand the distribution and occurrence of
False Killer whale along Central American
coastline based on photo-identification data
Etienne Pouplard, Lenin Oviedo,
David Herra-Miranda, Erika
Sanchez-Robledo, Joëlle De Weerdt
Occurrence and distribution
of False killer whales
(Pseudorca crassidens) in
Central America
Fig. 2: Example of quality 1
photo-identification pictures used for
our study. An example from Nicaragua
(Top) and an example from Costa
Rica (Bottom)
Fig. 3: Boxplot of Group sizes
between three study sites. P-value of
the Kruskal-Wallis test on the top right
corner and the p-value f the Pairwise
comparison test (Wilcoxon-mann test)
on the lines.
Fig. 1: Localization of the sightings in Nicaragua, Costa Rica, Panama.
METHODS
Boat Based effort with photo-identification:
Nicaragua
465 hours over 3 years (2016 - 2018)
Costa Rica
6100 hours over 14 years (2001 -2015)
Panama
6 opportunistic sighting (1999 – 2016)
For each sighting pictures, group size and
localization were recorded and analyzed with R.
RESULTS
Presence of False Killer whale in three Central
American Countries (Fig 1)
Total of 36 sightings (3, 27, 6)
Total of 5891 photos analyzed
Total of 68 Individuals identified (28, 40)
No resighting between Nicaragua and other
countries. No resighting within Nicaragua.
Resightings within the Nicoya Ecoregion:
within Costa Rica (n=12), and between Costa
Rica and Panama (n=2).
Significant difference in group size between
Costa Rica and Panama/Nicaragua (p-values
0.0021/ 0.01). No significant difference
between Panama & Nicaragua(p -values 0.6)
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... Photo ID analysis indicated the concurrent recapture of individuals from the OPW catalogue off Panama (LO data). Whereas a preliminary comparison with documented cases in Nicaragua has not yield any resighting of identified individuals (Pouplard et al., 2019), although a more in depth comparison is currently in progress. Based on the latter, we argue the potential occurrence of coastal population unit and oceanic island associated stock, as the one documented by Acevedo et al., (1997) off Isla del Coco. ...
Article
Full-text available
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 (2001-2019) 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.
... Photo ID analysis indicated the concurrent recapture of individuals from the OPW catalogue off Panama (LO data). Whereas a preliminary comparison with documented cases in Nicaragua has not yield any resighting of identified individuals (Pouplard et al., 2019), although a more in depth comparison is currently in progress. Based on the latter, we argue the potential occurrence of coastal population unit and oceanic island associated stock, as the one documented by Acevedo et al., (1997) off Isla del Coco. ...
Article
Full-text available
ABSTRACT. Introduction: False killer whales (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 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 (2001-2019) 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. Key words: Pseudorca crassidens; population size; capture-mark-recapture; demography, management-conservation, coastal-seascape
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