High site fidelity and restricted ranging patterns in southern Australian bottlenose dolphins

Abstract

Information on site fidelity and ranging patterns of wild animals is critical to understand how they use their environment and guide conservation and management strategies. Delphinids show a wide variety of site fidelity and ranging patterns. Between September 2013 and October 2015, we used boat‐based surveys, photographic identification, biopsy sampling, clustering analysis, and geographic information systems to determine the site‐fidelity patterns and representative ranges of southern Australian bottlenose dolphins (Tursiops cf. australis) inhabiting the inner area of Coffin Bay, a highly productive inverse estuary located within Thorny Passage Marine Park, South Australia. Agglomerative hierarchical clustering (AHC) of individuals’ site‐fidelity index and sighting rates indicated that the majority of dolphins within the inner area of Coffin Bay are “regular residents” (n = 125), followed by “occasional residents” (n = 28), and “occasional visitors” (n = 26). The low standard distance deviation indicated that resident dolphins remained close to their main center of use (range = 0.7–4.7 km, X ± SD = 2.3 ± 0.9 km). Representative ranges of resident dolphins were small (range = 3.9–33.5 km2, X ± SD = 15.2 ± 6.8 km2), with no significant differences between males and females (Kruskal–Wallis, χ2 = 0.426, p = .808). The representative range of 56% of the resident dolphins was restricted to a particular bay within the study area. The strong site fidelity and restricted ranging patterns among individuals could be linked to the high population density of this species in the inner area of Coffin Bay, coupled with differences in social structure and feeding habits. Our results emphasize the importance of productive habitats as a major factor driving site fidelity and restricted movement patterns in highly mobile marine mammals and the high conservation value of the inner area of Coffin Bay for southern Australian bottlenose dolphins.

Photographic Capture-Recapture Analysis Reveals a Large Population of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) With Low Site Fidelity off the North West Cape, Western Australia

“…We investigated the monthly, sampling period, and yearly sighting rates of individuals to determine the tendency of dolphins to return to the study area (Zanardo et al, 2016;Hunt et al, 2017;Passadore et al, 2018).…”

“…Within a population, individuals have been observed showing varying levels of residency with individuals typically characterized as residents, migratory (semi-resident) or transient (non-resident). High levels of site fidelity and residency are characteristic of bottlenose dolphins in protected coastal areas with high prey availability and low predation risk (Gowans et al, 2007;Fury and Harrison, 2008;Chabanne et al, 2012;Webster et al, 2014;Brown et al, 2016;Zanardo et al, 2016;Dulau et al, 2017;Passadore et al, 2018). In contrast, low levels of site fidelity is often typical of individuals inhabiting lower productivity areas where prey availability is highly variable in space and time (Gowans et al, 2007;Silva et al, 2008;Edwards et al, 2009;Lafontaine et al, 2017).…”

Kinship and reproductive condition correlate with affiliation patterns in female southern Australian bottlenose dolphins

“…australis 46 ) inhabiting the inner area of Coffin Bay, South Australia, a heterogeneous inshore environment composed of small bays and channels. Coffin Bay is considered a stronghold for southern Australian bottlenose dolphins, with high densities of dolphins reported (1.57-1.70 dolphins/km 2 47 ), similar male-to-female ratio of non-calf individuals (males = 46-52; females = 52-60 47 ), and restricted ranging patterns by both sexes 48 . The majority of females in Coffin Bay had representative ranges (95% kernel ranges) smaller than 15 km 2 (mean representative range = 14.7, SD = 7.0 km 2 ), and most (56%) showed ranging patterns restricted to a particular bay 48 .…”

“…Coffin Bay is considered a stronghold for southern Australian bottlenose dolphins, with high densities of dolphins reported (1.57-1.70 dolphins/km 2 47 ), similar male-to-female ratio of non-calf individuals (males = 46-52; females = 52-60 47 ), and restricted ranging patterns by both sexes 48 . The majority of females in Coffin Bay had representative ranges (95% kernel ranges) smaller than 15 km 2 (mean representative range = 14.7, SD = 7.0 km 2 ), and most (56%) showed ranging patterns restricted to a particular bay 48 . The Coffin Bay dolphin population is socially structured into two communities with discrete core ranges, where individuals from the same communities are on average more bi-parentally related than individuals from different communities 49 .…”

Using cost-effective surveys from platforms of opportunity to assess cetacean occurrence patterns for marine park management in the heart of the Coral Triangle

“…Consequently, both species were recorded as bottlenose dolphin (Tursiops spp). Bottlenose dolphins are known to form stable social groups, sometimes with small resident populations that have a high affiliation to a relatively small area (Dulau et al, 2017;Passadore et al, 2018a;Shirakihara et al, 2002). These populations seem to be linked to coastal areas that have high prey availability and low predation risk (Haughey et al, 2020).…”