Bottlenose dolphinTursiops truncatusgroup dynamics, site fidelity, residency and movement patterns in the Madeira Archipelago (North-East Atlantic)

Abstract

The bottlenose dolphin Tursiops truncatus is one of the most frequently sighted cetacean species in the Madeira Archipelago (North-East Atlantic); however, little is known about its population ecology in these waters. Photo-identification undertaken during systematic, non-systematic and opportunistic surveys conducted between 2001 and 2012 was used to assess group dynamics, site fidelity, residency and movement patterns of bottlenose dolphins in the archipelago. Three different patterns of residency were assigned, based on individual sighting histories. Group size ranged between 2 and 90 individuals (median 12), with no significant monthly difference in group size. All resident dolphins formed a core, complex network with migrant and transient dolphins. In contrast, satellite clusters were formed exclusively by transient individuals. The lagged identification rate (LIR) model indicated that a dolphin remained in the area for an average of 90 days, whereas the average time an individual spent outside the study area was approximately 313 days. The Madeira Archipelago appears to be only a section of a much larger home range for this population, with the dolphins exhibiting three different patterns of occurrence that associate with each other. The information gained about this poorly studied population contributes to the overall knowledge of bottlenose dolphins in insular oceanic habitats.

Analysis of occurrence patterns and biological factors of cetaceans based on long‐term and fine‐scale data from platforms of opportunity: Madeira Island as a case study

“…Arcangeli et al, ; Hupman et al, ) by demonstrating that despite their limitations, platforms of opportunity, and specifically whale‐watching vessels, constitute highly cost‐effective tools and valuable vehicles that can provide robust data sets. The similarity of the values presented in this study to those from dedicated surveys for the proportion of calves, group sizes, and inter‐specific relationships in Globicephala macrorhynchus and Tursiops truncatus in Madeira (Alves, ; Dinis, Alves, et al, ) supports the reliability of the results obtained from platforms of opportunity. These vehicles should be used to collect baseline information on species occurrence, diversity, and group dynamics, which can help to answer numerous questions regarding the conservation of marine mammals.…”

“…In particular, S. frontalis and the deep‐diver species Mesoplodon densirostris and G. macrorhynchus were observed with calves in a high percentage (>40%) of the groups, and in the latter case the calves were present throughout the year, which is consistent with another study (Alves, ). Similar results for the proportion of groups with calves in T. truncatus were also found between this (24%) and an independent data set from a similar period and region (26.4%, Dinis, Alves, et al, ). The importance of this area as a calving ground is also supported by the observation of births/neonates in Madeiran waters for some of these species, such as S. frontalis (Alves, Nicolau, Dinis, Ribeiro, & Freitas, ), G. macrorhynchus (Reggente et al, ) and P. macrocephalus (Correia‐Fagundes & Romano, ).…”

“…Stenella frontalis and B. brydei were amongst the species with the highest mean occurrence rate across the 11 years of the present study, and yet these species were only first recorded in Madeira in 1997 and 2003, respectively (Freitas, Dellinger, & Reiner, ; Freitas et al, ). The study also found that Tursiops truncatus and G. macrorhynchus were amongst the most sighted species, which is in accordance with the existence of island‐associated populations in Madeira (Alves, Dinis, et al, ; Dinis, Alves, et al, ). Together with Delphinus delphis , these five species comprise the majority (87%) of the sightings in Madeira, contrasting with Tenerife (Canary Islands, which lies about 300 km south of Madeira) where T. truncatus and G. macrorhynchus together comprise 82% of all sightings (Carrillo et al, ).…”

“…Yet, here, ecological and biological studies exist only for specific species (e.g. Alves, Dinis, Cascão, & Freitas, ; Alves, Dinis, et al, ; Alves, Quérouil, et al, ; Dinis, Carvalho, et al, ; Dinis, Alves, et al, ; Quérouil et al, , ), and therefore information on cetacean community structure remains widely unknown. In addition, there is an increasing number of anthropogenic activities in Madeira with potential impacts on cetaceans, in particular the whale‐watching industry (Alves, Dinis, et al, ; Ferreira, ) and marine traffic (Cunha et al, ).…”

Temporal–spatial distribution of an island‐based offshore population of common bottlenose dolphins (Tursiops truncatus) in the equatorial Atlantic

“…Population monitoring in Madeira provided evidence that the local area is only a section of a much larger home range for the North Atlantic population (Dinis et al 2016). Additionally, the lack of population structure in the archipelagos of Madeira and Azores are indicative of the importance of oceanic bottlenose dolphins of the Northwest Atlantic, which are able to maintain high gene flow (Qu erouil et al 2007).…”