First estimate of common bottlenose dolphin (Tursiops truncatus) (Cetacea, Delphinidae) abundance off Uruguayan Atlantic coast

Abstract

The common bottlenose dolphin Tursiops truncatus is often observed throughout the oceanic coast of Uruguay. Historically, its distribution was wider, including the estuary of the Río de la Plata, but currently its occurrence seems to be restricted mainly to the Uruguayan Atlantic coast (Rocha Department). Conflicting interests and tradeoffs between conservation and development are being generated in Uruguay. On one hand, the establishment of protected areas, responsible tourism and sustainable fisheries are promoted, while on the other hand, foreign exploitation of natural resources and development of mega-infrastructure in coastal zone are facilitated. In this work, we provide the first estimate of bottlenose dolphin’s abundance along the Uruguayan Atlantic coast. These results can be used as baseline information for monitoring population trends and guiding conservation actions for bottlenose dolphins in Uruguay. Mark-recapture models were applied to data of photoidentified animals with long-lasting natural marks. Total population size estimates of 63 individuals (95% CI = 54–74) and 61 (95% CI = 53–73) were obtained from closed and open population models, respectively. Although the estimates are within the range of values obtained for other coastal bottlenose dolphin populations in the Southwest Atlantic Ocean, as well as other regions of the world, it is lower than the values reported for populations inhabiting open habitats. This small population is probably vulnerable to non-natural removals, environmental and demographic stochasticity. Therefore, precautionary actions are recommended given the planned development for this coastal region.

Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

“…On the other hand, remarkably low levels of genetic diversity for the coastal ecotype likely reflects small population sizes of possibly a few hundred individuals (Fruet, Flores, et al., ; Fruet, Zappes, et al., ). Mark‐recapture data from long‐term studies of coastal populations along the SWA indicate critical small population sizes (populations not exceeding 90 individuals) and high site fidelity of individuals (e.g., Daura‐Jorge, Ingram, & Simões‐Lopes, ; Fruet, Daura‐Jorge, Möller, Genoves, & Secchi, ; Giacomo & Ott, ; Laporta, Fruet, et al., ; Vermeulen & Cammareri, ).…”

“…These coastal populations are small (<100 individuals) and associated with estuaries, river mouths, and lagoons (see Simões‐Lopes, ; Lodi et al., ; Laporta, et al., ; Fruet, Flores, & Laporta, ; Fruet et al., ; for reviews). Sighting data suggest no movement of coastal bottlenose dolphins to deep waters (i.e., >20 m depth), although movements of individuals between coastal areas frequently occur (Würsig, ; Simões‐Lopes & Fábian, ; Laporta, Di Tullio, et al., ; Laporta, Fruet, & Secchi, ). Recent studies have shown remarkably low levels of genetic diversity and strong genetic differences among these coastal populations at both microsatellites and mitochondrial DNA markers (Costa et al., ; Fruet et al., ).…”

Movements and habitat use of bottlenose dolphins,Tursiops truncatus, in south-eastern Brazil

“…(2016) suggested that the species has a continuous distribution along the Brazilian coast, which varies in depth from 1.6–50 m, as reported by Laporta et al . (2016). The group sizes detected in the present work (mean 39 ± 22 individuals, N = 13) were higher than those previously observed in other regions of the Brazilian coast.…”

Echolocation inter-click interval variation among specific behaviours in free-ranging bottlenose dolphins from the coast of Uruguay

“…Bottlenose dolphins occur year-round in the Atlantic coastal waters of Uruguay, using the coastal zone mainly for feeding, socialising and reproduction (Fruet et al, 2014;Laporta et al, 2016;Menchaca et al, 2019;Ott et al, 2016;Tellechea et al, 2014). Groups are variable in size and age composition, ranging from one to 30 individuals, with larger groups also including calves (Laporta et al, 2016;Menchaca et al, 2019;Tellechea et al, 2014).…”