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Shark attacks on bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia: Attack rate, bite scar frequencies, and attack seasonality

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Abstract

Shark predation may have been a central factor influencing the evolution of sociality in dolphins, as well as a determinant of dolphin habitat use and behavior. To understand the role of predation in driving interpopulation differences in behavior and sociality, it is important to quantify differences in predation risk among populations. This study describes the frequency of shark-inflicted scars and estimates the shark attack rate on bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia. Shark bite scars were found on 74.2% (95 of 128) of non-calves, and most of these scars were inflicted by tiger sharks (Galeocerdo cuvier). Although there were no differences among age/sex classes in the frequency of scarring, significantly more adult males than adult females bore multiple scars. The rate of unsuccessful shark attack was estimated to be between 11% and 13% of dolphins attacked each year. Large sharks (>3 m) were responsible for a disproportionate number of attacks. However, bites from small carcharhinid sharks on 6.2% of dolphins suggest that some of these small sharks may be dolphin ectoparasites. Both the scar frequencies and attack rate suggest that Shark Bay dolphins face a greater risk of predation than bottlenose dolphins in other locations.

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... Therefore, injuries were assessed for the dorsal surface only and not for the ventral side of the dolphins. For the injury assessment, two independent observers examined each individual's photographs, extracted scars that were crescent-shaped and analyzed them visually to judge if it could have been shark-inflicted (Fearnbach et al., 2011;Heithaus, 2001b;Lowry et al., 2009;Figure 2a). The location of each injury on the dolphin body was recorded as: anterior (between the blowhole and the dorsal fin), left or right flank, or peduncle (between the dorsal fin and the flukes, Figure 2a). ...
... Injuries were found on all examined body regions, including the anterior part, flanks, and peduncle. In line with some previous studies in which scars on the head, dorsal fin, or flukes were rare, if observed at all (Heithaus, 2001b;Luksenburg, 2014;Smith et al., 2018), no scar was found on these body parts in the present study. The body areas documented in this study were dorsal, therefore ventral injuries could not be recorded. ...
... Dorsal wounds may be less severe, and dolphins may be able to survive and heal (e.g., Orams & Deakin, 1997), explaining the prevalence of dorsal scars relative to ventral injuries. Turning their back to sharks has even been proposed as a strategy to protect dolphins' ventral side (Heithaus, 2001b). ...
... Due to the ecological importance of water depth reported in other coastal bottlenose dolphin habitat use studies (Heithaus andDill, 2002, 2006;Zanardo et al., 2017;Passadore et al., 2018;Sprogis et al., 2018a;Vargas-Fonesca et al., 2018), water visibility was dropped from all SDMs as an explanatory variable. Additional correlation testing (after the removal of water visibility), revealed no further collinearity within the seasonal and overall datasets. ...
... Both prey availability and predation risk are known to influence dolphin distribution and habitat use (Heithaus andDill, 2002, 2006;Wirsing et al., 2008). Predictor variables used in ensemble models in our study (i.e., water depth, seabed slope, and SST) often represent proxies for prey distribution and predation risk, influencing dolphin distribution elsewhere (Heithaus and Dill, 2002;Ingram and Rogan, 2002;Zanardo et al., 2017;Sprogis et al., 2018a). ...
... Predictor variables used in ensemble models in our study (i.e., water depth, seabed slope, and SST) often represent proxies for prey distribution and predation risk, influencing dolphin distribution elsewhere (Heithaus and Dill, 2002;Ingram and Rogan, 2002;Zanardo et al., 2017;Sprogis et al., 2018a). Occurrence is often a tradeoff between prey availability and predation pressure, and future studies looking further into diet, associated prey availability, and predation pressure are needed to assess the degree of influence these have on dolphin distribution at the NWC, as has been explored in other areas of Western Australia (WA) (Heithaus, 2001;Heithaus and Dill, 2002;McCluskey et al., 2016;Smith et al., 2018;Sprogis et al., 2018b). ...
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Assessments of species distributions are crucial for informing conservation and management action. In this study, we used ensemble modelling to explain the distribution of Near Threatened Indo-Pacific (IP) bottlenose dolphins (Tursiops aduncus) in coastal waters at the North West Cape (NWC), Western Australia (WA), an area encompassing a marine protected area (MPA) and adjacent unprotected coastal waters. Analyses used dolphin sighting data collected during boat-based surveys conducted from 2013 to 2015 and 2018 to 2019. Overall, the distribution of IP bottlenose dolphins was best explained by distance to coast (up to 2,000 m) and distance to boat ramp (up to 7,000 m). Areas of high probability of occurrence for dolphins extended from the tip and down the eastern side of the NWC and overlapped with designated sanctuary zones as well as waters beyond the boundaries of the Ningaloo Marine Park (NMP). Distribution and habitat preferences varied slightly with season. In autumn, dolphin distribution was best explained by distance to coast and water depth with a higher likelihood of observing dolphins 1,000–2,000 m from the coast and in water depths of 7–10 m deep. During winter months, distance to coast (1,000–2,000 m) and sea surface temperature (SST) (21.5–23.5°C) were the most important explanatory variables, with presence in coastal lagoons to the west of the NWC more likely than other seasons. During spring, areas of moderate to high probability of dolphin occurrence were mainly located outside the NMP, with marine park zone (outside the NMP and Sanctuary zones within the NMP, the two zones with the highest probability of IP bottlenose dolphin occurrence) and water depth (waters 7–13 m deep) best explaining dolphin distribution. This study highlights the importance of inshore areas of the NWC for IP bottlenose dolphins and the potential vulnerability of this species to increasing and cumulative anthropogenic stressors associated with these areas. Results of this study should be considered in future zoning reviews and adaptive management efforts of the NMP allowing for effective management of this Near Threatened species.
... This approach is not exclusive to small cetaceans, e.g., it has been applied to manta rays (Manta alfredi; Marshall & Bennett, 2010), green (Chelonia mydas) and loggerhead sea turtles (Caretta caretta ;, and leatherback sea turtles (Dermochelys coriacea; Archibald & James, 2018). Among dolphins, it has most commonly been used with well-studied populations of bottlenose dolphins (Tursiops aduncus; Corkeron et al., 1987a;Heithaus, 2001b;Heithaus et al., 2017;Sprogis et al., 2018;T. truncatus;Wilkinson et al., 2017), but also Australian snubfin (Orcaella heinsohni) and Australian humpback dolphins (Sousa sahulensis; Smith et al., 2018), Guiana dolphins (Sotalia guianensis; Santos & Gadig, 2009), and Atlantic spotted dolphins (Stenella frontalis; Melillo-Sweeting et al., 2014). ...
... Individuals not in the catalog were excluded to ensure each individual was only counted once. Crescent-shaped injuries and deep, widely spaced tooth rakes were categorized as shark-induced (Heithaus, 2001b). Jagged injuries to the dorsal or pectoral fins were also classified as shark-related (Melillo-Sweeting et al., 2014). ...
... Bites were also marked for their location on the dolphin's body according to three main regions: dorsal (including dorsal fin), ventral, or extremity (rostrum, pectoral fins, and fluke). The number of individuals with shark-induced scars is considered a minimum estimate, given the bias toward the dorsal side in boat-based surveys and the potential of old, well-healed injuries to be missed (Heithaus, 2001b), as well as different sighting rates for individuals (Sprogis et al., 2018). ...
Article
Shark predation risk impacts many facets of dolphin life, including habitat use and foraging strategies. Because direct predation is rarely observed, researchers instead examine dolphins in situ for past injuries that can be attributed to sharks. We analyzed existing photo‐ID catalogs of common bottlenose (Tursiops truncatus) and Atlantic spotted dolphins (Stenella frontalis) off Bimini, The Bahamas. A minimum of 29% of individual T. truncatus had evidence of a past, nonlethal shark bite, while for S. frontalis this was only 15%. For both species, shark‐induced injuries were predominantly on the dorsal side. Regression analyses indicated that T. truncatus were more likely to have shark bite scars than S. frontalis and the likelihood of documenting a shark bite scar increased with a higher percentage of the body photographed. T. truncatus were less likely to have scars in the dorsal region, but sampling differences could have influenced these results. While the shark species responsible for scars was not determined, T. truncatus and S. frontalis overlap spatially and temporally with tiger (Galeocerdo cuvier) and bull sharks (Carcharhinus leucas) off Bimini. This study builds on the understanding of dolphin/shark interactions from longitudinal studies of dolphins in this region, providing insight into factors influencing predation risk.
... Several studies have suggested that predation attempts (e.g. scars and other injuries) could be used to gain insights into predation risk or pressure to a wide range of taxa, including coastal dolphins (Heithaus 2001b;Smith et al. 2018 (Paris & Chérubin 2008). Many productive ecosystems are part of the MARS including coral reefs, seagrass beds, and mangrove areas, which provide critical habitats for many species and coastal fisheries. ...
... For each obtained photograph, we examined the visible areas of the animals for scarring and/or injuries likely resulting from shark bites, primarily the dorsal surface of the dolphin from its blowhole to caudal peduncle. A shark-related injury was identified by their crescent-shaped wound pattern, consisting of deep and widely spaced teeth rakes (different from those caused by a conspecific, for example) (Heithaus 2001b) or small round or oval scooped-out wounds consistent with injuries caused by cookiecutter sharks (Dwyer & Visser 2011). Injuries or scarring was described in terms of location on the body and healing state. ...
... We observed that all the scars inflicted by sharks were located on the body trunk area (anterior peduncle, flank), while no bites were found in tail/peduncle, dorsal fin, and head zones. These findings are similar to previous reports for bottlenose dolphins in several regions (Heithaus 2001b;Luksenburg 2014;Smith et al. 2018). However, the calculated proportions are based on relatively small sample sizes across our sampled site and most photos of dolphins cover the dorsal surface of the animal and rarely the tail or ventrum. ...
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Understanding predator-prey relationships is critical in ecology, but relatively challenging when investigating elusive marine megafauna. In this study, we document the presence of shark-inflicted injuries on coastal bottlenose dolphins (Tursiops truncatus) in the Mesoamerican Reef System using photo-identification methods. We analyzed data from a total of 533 photo-identified bottlenose dolphins in Mexico (Ascención Bay, Espíritu Santo Bay, and Chetumal Bay), Belize (Turneffe Atoll, Drowned Cayes, Barrier Reef, and Placencia), and Honduras (Utila). We identified 16 individuals with shark-inflicted injury scars consistent with attacks by large sharks of the Family Carcharhinidae. Additionally, two bottlenose dolphins were encountered with round-shaped crater wounds, likely inflicted by a cookiecutter shark (Isistius spp.). The prevalence of shark-inflicted wounds in bottlenose dolphins varied markedly between sites, with the highest prevalence in Placencia and Ascención Bay (Mexico), and lowest in Turneffe Atoll and Drowned Cayes (Belize). Further research is required to evaluate how predation risk shapes the ecology of bottlenose dolphins in the Mesoamerican Reef region.
... In contrast, shark bites are common on bottlenose https://doi.org/10.1016/j.jembe.2018.08.008 Received 9 January 2018; Received in revised form 1 July 2018; Accepted 26 August 2018 dolphins (Tursiops aduncus) in Shark Bay, Australia, with 74.2% of noncalf dolphins bearing wounds (Heithaus, 2001b). However, there are several caveats in using wounds and scars as an indication of predation rate (Heithaus, 2001a;Heithaus et al., 2017). ...
... However, there are several caveats in using wounds and scars as an indication of predation rate (Heithaus, 2001a;Heithaus et al., 2017). For example, as wounds and scars represent failed predation attempts, the true frequency of shark attacks is usually unknown and would be higher than that measured by non-lethal, wound frequencies (Heithaus, 2001b). Nevertheless, comparisons among similar dolphin species and populations provide a useful, relative index of predation pressure (Heithaus, 2001a). ...
... Large predatory sharks feed generally with an open-mouthed, ram-feeding strike (Corn et al., 2016;Motta and Wilga, 2001). Hence, wounds or scars on dolphins that were crescent-shaped and with deep craters or messy lacerations, were considered as evidence of a shark interaction (Heithaus, 2001b;Lowry et al., 2009). As dolphins typically only showed their dorsal region upon surfacing, observations and photographs were of this region (from the head to the upper flanks). ...
... Evidence of shark bites on bottlenose dolphins (Tursiops spp.) has been reported from the open ocean (Wood et al. 1970), and several coastal locations, including: Moreton Bay, Queensland (Corkeron et al. 1987); Natal, South Africa (Cockcroft et al. 1989); Shark Bay, Western Australia (Heithaus 2001b); the Bahamas (Fearnbach et al. 2012), and various locations in the southwestern Indian Ocean (Heithaus et al. 2017 Three species of dolphin cooccur in the shallow, coastal waters of northwestern Australia: the Australian snubfin dolphin (Orcaella heinsohni, hereafter "snubfin dolphin"), the Australian humpback dolphin (Sousa sahulensis, hereafter "humpback dolphin"), and the Indo-Pacific bottlenose dolphin (Tursiops aduncus, hereafter "bottlenose dolphin") (Allen et al. 2012). Snubfin and humpback dolphins are endemic to the tropical inshore waters of northern Australia and southern New Guinea (Beasley et al. 2005, Jefferson andRosenbaum 2014), and are sympatric throughout most of their distribution in Australia (Parra et al. 2002(Parra et al. , 2004. ...
... Comparative studies on the east coast of Australia have revealed small population sizes, fine-scale habitat partitioning, and differences in grouping and association patterns between the two species (Parra 2006;Parra et al. 2006Parra et al. , 2011. Shark predation risk to bottlenose dolphins is considerable in the subtropical waters of Shark Bay, Western Australia (Heithaus 2001b), but such insights are lacking for any species off tropical northern Australia. ...
... This served to standardize the comparison of shark bite prevalence between dolphins, and ensure that bite prevalence was not biased towards individuals with greater photographic coverage. These body areas were selected as they were most readily photographed when animals surfaced, have been documented to display the highest frequency of shark bites (Heithaus 2001b), and provide a suitable compromise between unbiased estimates of bite prevalence and a representative sample size. ...
Article
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Predation risk has a profound influence on the behavior of marine mammals, affecting grouping patterns and habitat use. Dolphins frequently bear evidence of shark bites, which can provide an indirect measure of predation pressure. Using photo-identification data, we investigated the prevalence of shark bites on three sympatric species of inshore dolphin, the Australian snubfin (Orcaella heinsohni), Australian humpback (Sousa sahulensis), and Indo-Pacific bottlenose dolphin (Tursiops aduncus), among four study sites in northwestern Australia. Bite prevalence varied markedly between species, with 72% of snubfin, 46% of humpback, and 18% of bottlenose dolphins exhibiting evidence of shark bites. Binomial logistic regression confirmed a high likelihood of bite presence on snubfin dolphins, and at one particular site for snubfin and bottlenose dolphins. The prevalence of tiger shark (Galeocerdo cuvier) bites on snubfin dolphins was high, and bites attributed to other carcharhinid sharks were observed on all species. While acknowledging methodological differences with other studies, the prevalence of shark bites on snubfin dolphins is among the highest reported for any dolphins, suggesting predation risk represents an important but varying influence thereon. This study provides a baseline for future investigations into the affect of predation risk on the behavioral ecology of these sympatric species.
... Photographs were also used to examine individuals for evidence of scars from shark bites. Scars were considered to have been inflicted by sharks if they were characteristically crescent-shaped or had deep and widely spaced tooth marks (Heithaus, 2001). We determined the proportion of individuals with wounds by comparing the number of known individuals with wounds to the total number of individuals identified. ...
... We determined the proportion of individuals with wounds by comparing the number of known individuals with wounds to the total number of individuals identified. This method underestimates the actual proportion of individuals with wounds since only a small portion of the body is surveyed for evidence of shark bites (Heithaus, 2001). ...
... The proportion of individuals with scars or wounds from shark bites was quite low (1 -5%) compared with some other locations. For example, boat-based observations of freeswimming animals documented scars of 74.2% of individuals in Shark Bay (Heithaus, 2001) and 36.6% of individuals in Moreton Bay, Australia (Corkeron et al., 1987). In Sarasota Bay, the proportion of individuals with shark-inflicted wounds is lower. ...
Article
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Bottlenose dolphins ( Tursiops truncatus ) are abundant in many coastal ecosystems, including the coastal Everglades. Understanding spatial and temporal variation in their abundance and group sizes is important for estimating their potential ecological importance and predicting how environmental changes (e.g. ecosystem restoration) might impact their populations. From August 2010 to June 2012, we completed a total of 67 belt transects covering a total of 2650 linear km and an area of 1232 km ² . Dolphin densities varied spatially and temporally. The highest densities of dolphins were found in coastal oceans and inland bays and were lowest in rivers. Use of rivers, however, increased during the dry season while densities in other habitats remained similar across seasons. Dolphins appeared to prefer portions of bays close to mangrove-covered islands over open waters. A resighting rate of 63.6% of individuals across the 2-year study suggests that at least a portion of the population is probably resident within study regions over long time periods. The largest groups (mean 6.28, range 1–31) were found in open waters and bays despite apparently low predation pressure. Indeed, shark bite scars – likely the result of unsuccessful predation attempts – were conclusively observed on only 1% of individuals. Although further studies are warranted, the high densities of dolphins suggest that they are an important upper trophic level predator in the coastal Everglades, but their ecological importance probably varies in space and time.
... However, the low proportion of large crescent-shaped scars in dolphins in the study area suggests that predation pressure is extremely low. Over the years, only three of 143 identified animals (2%) from four different dolphin communities showed evidence of scars associated with predation similar to those left by sharks (e.g., Corkeron et al., 1987;Heithaus, 2001). This proportion is much lower compared to bottlenose dolphins in Florida (22%) (Wells et al., 1987) and 74.2% in the Indo-Pacific bottlenose dolphin (Heithaus, 2001). ...
... Over the years, only three of 143 identified animals (2%) from four different dolphin communities showed evidence of scars associated with predation similar to those left by sharks (e.g., Corkeron et al., 1987;Heithaus, 2001). This proportion is much lower compared to bottlenose dolphins in Florida (22%) (Wells et al., 1987) and 74.2% in the Indo-Pacific bottlenose dolphin (Heithaus, 2001). The preferential use of shallow areas during the season of abundance of the bull shark (Carcharhinus leucas) has been observed in common bottlenose dolphins in Sarasota Bay, Florida (e.g. ...
Article
The habitat use by two neighboring coastal bottlenose dolphin communities (Posorja and El Morro) was eval�uated in the western inner estuary of the Gulf of Guayaquil, Ecuador (3◦S, 80◦55′ W). The study aimed to determine to what extent some environmental variables influence dolphins’ distribution and behavior. The analysis included 344 dolphin groups recorded between 2014 and 2019. For both dolphin communities, 95% of home ranges were estimated (23.5 km2 Posorja and 44.8 km2, El Morro). Home ranges overlapped in an area of 11.2 km2. No clear preference for areas to carry out specific activities was found, as dolphins used the same areas for multiple purposes. Multinomial logistic regression with four environmental parameters (distance to shore, depth, hour of day and tide) were used as predictor variables of behavior. A significant relationship between the tidal cycle and behavioral states was found with feeding occurring more frequently during the low tide, so�cializing and transit during high tide, and resting during mid-tide. Count models were used with environmental and behavioral variables to explore their relationship with dolphins’ group size. Differences with respect to dolphin counts were associated with tide height and socialization. Depth is relevant for predicting dolphin counts mainly during high tide. We recommend that environmental authorities consider the dolphins’ preference to carry out their activities within small home ranges, identify overlapping human activities and take steps to reduce potential conflicts, such as prohibiting all types of gillnets in areas of high concentration of dolphins. Likewise, regular assessments are required to detect future changes in both dolphins’ habitat and human uses over time.
... The presence of sublethal injuries is not thought to substantially impair reproductive capacity, unless the reproductive organs are damaged (Jessop et al., 2004;Andersen et al., 2008;Wells et al., 2008;Germanov et al., 2019). However, it is unclear whether injury has an impact on the rate of reproduction or level of reproductive success, which could have implications for population health (Heithaus, 2001b;Andersen et al., 2008;Wells et al., 2008). For example, major injuries to an organism can delay the age at sexual maturity (Harris, 1989), and physiological stress (e.g., from capture or entanglement) can lead to abortion in elasmobranchs (Adams et al., 2018). ...
... However, R. typus individuals are highly migratory (Hearn et al., 2016), so healed predation injuries could have occurred in other locations within their range (Speed et al., 2008). Studies investigating shark bite scarring frequencies in dolphins (e.g., Tursiops spp.) have suggested predation pressure may be influenced by the availability of other shark prey (Heithaus, 2001a;Smith et al., 2018), spatial and temporal overlap of dolphins and sharks (Melillo-Sweeting et al., 2021), similar habitat selection (e.g., the use of sheltered semi-enclosed waters) (Sprogis et al., 2018), reduced fishing pressure for large sharks (Castelblanco-Martínez et al., 2021), or differences in dolphin and shark species or sizes, and the resulting probability of a lethal shark encounter (Heithaus, 2001b;Heithaus et al., 2017;Wilkinson et al., 2017). ...
Article
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Manta ray populations worldwide are vulnerable to sublethal injuries resulting from human activities, e.g., entanglement in fishing line and boat strikes, which have the potential to impact an individual’s health, fitness, and behaviour. Sublethal injuries and physical abnormalities also occur naturally from predation events, deformity, parasites, and disease. To determine the type and frequency of anthropogenic and natural originated injury events affecting Mobula alfredi and M. birostris in the Maldives, we examined data from the Manta Trust’s Maldivian Manta Ray Project (MMRP) database, which contains 73,638 photo-identification (photo-ID) sightings of the two manta ray species from 1987 to 2019. The likely origin of each injury or physical abnormality was determined based on visual assessment of the photo-ID images. Multiple injuries to an individual originating from the same event were grouped for analysis. Generalised linear mixed models (GLMM) were used to investigate the relationship between the occurrence of injury events and the explanatory variables sex and maturity status for both species, with the additional variable site function (cleaning, feeding, cruising) investigated for M. alfredi. Spatial and temporal variations in M. alfredi injury events, and their origin and type, were investigated by calculating the percentage of injury events per sighted individual at each Maldivian atoll, and per re-sighted individual in each year from 2005 to 2019. For both species, injury events were predominantly of natural origin, with predatory bites being the most frequent type. The most common anthropogenic injury type was entanglement in fishing line. Injuries to M. alfredi were significantly more likely to be observed on juveniles than adults, males than females, and at cleaning stations as opposed to feeding or cruising sites. Neither sex nor maturity status were significant explanatory variables for the occurrence of injuries to M. birostris. Highest percentages of anthropogenic injuries per sighted M. alfredi were recorded in North Malé, South Malé, Baa, Addu, and Laamu Atolls, where boat traffic, fishing, and tourism activities are concentrated. Overall, this work greatly improves understanding of the sublethal threats faced by manta rays in the Maldives; identifying focus areas where conservation management actions are required to ensure more effective protection of this threatened species group.
... The primary threat to Shark Bay dolphins is the tiger shark (Galeocerdo cuvier), based on lethal attacks (Mann and Barnett, 1999), scarring patterns and prevalence on dolphins (Heithaus, 2001a), and that 94% of large sharks caught during shark fishing research were tiger sharks (Heithaus, 2001b). Though we cannot accurately measure lethal predation events due to insufficient carcass recovery, prior work in Shark Bay suggests that non-lethal attacks are common; over 74% of non-calf individuals bear scars from non-fatal shark attacks (Heithaus, 2001a). ...
... The primary threat to Shark Bay dolphins is the tiger shark (Galeocerdo cuvier), based on lethal attacks (Mann and Barnett, 1999), scarring patterns and prevalence on dolphins (Heithaus, 2001a), and that 94% of large sharks caught during shark fishing research were tiger sharks (Heithaus, 2001b). Though we cannot accurately measure lethal predation events due to insufficient carcass recovery, prior work in Shark Bay suggests that non-lethal attacks are common; over 74% of non-calf individuals bear scars from non-fatal shark attacks (Heithaus, 2001a). We therefore used scarring rates as a proxy for shark predation pressure, which we hypothesized may have increased following the reduction in other shark prey species (Nowicki et al., 2019). ...
Article
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As demands for wildlife tourism increase, provisioning has become a popular means of providing up-close viewing to the public. At Monkey Mia, Shark Bay, Australia, up to five adult female Indo-Pacific bottlenose dolphins ( Tursiops aduncus ) visit a 100 m stretch of beach daily to receive fish handouts. In 2011, a severe marine heatwave (MHW) devastated seagrass and fish populations in Shark Bay. Offspring survival declined precipitously among seagrass specialists (dolphins that forage disproportionately in seagrass habitat). As all provisioned dolphins at the site are seagrass specialists, we examined how provisioned and non-provisioned seagrass specialists responded to the MHW. Using 27 years of data we compare habitat use, home range size, calf mortality, and predation risk between provisioned and non-provisioned females and their offspring before and after the MHW. Our results show that provisioned females have extremely small home ranges compared to non-provisioned females, a pattern attributable to their efforts to remain near the site of fish handouts. However, weaned offspring (juveniles) born to provisioned females who are not provisioned themselves also had much smaller home ranges, suggesting a persistent maternal effect on their behavior. After the MHW, adult females increased their use of seagrass habitats, but not their home range size. Provisioned females had significantly lower calf mortality than non-provisioned females, a pattern most evident pre-MHW, and, in the first 5 years after the MHW (peri-MHW, 2011–2015), calf mortality did not significantly increase for either group. However, the ecosystem did not recover, and post-MHW (2016–2020), calf mortality was substantially higher, regardless of provisioning status. With few survivors, the impact of the MHW on juvenile mortality post-weaning is not known. However, over three decades, juvenile mortality among offspring of provisioned vs. non-provisioned females did not statistically differ. Thus, the survival benefits accrued to calves in the provisioned group likely cease after weaning. Finally, although shark attack rates on seagrass specialists did not change over time, elevated predation on calves cannot be ruled out as a cause of death post-MHW. We discuss our results as they relate to anthropogenic influences on dolphin behavioral plasticity and responses to extreme climate events.
... None of these were related to cookiecutter sharks (Isistius sp.), which is consistent to the known pelagic habitat of these shark species. Estimating which shark species may predate on Indo-Pacific bottlenose dolphins remains challenging (Heithaus, 2001;Smith et al., 2018;Sprogis et al., 2018b). In New Caledonia, large species of sharks such as tiger sharks (Galeocerdo cuvier) or bull sharks (Carcharhinus leucas) are present in the lagoon and are known to be involved in attacks on dolphins (Heithaus et al., 2017). ...
... In New Caledonia, large species of sharks such as tiger sharks (Galeocerdo cuvier) or bull sharks (Carcharhinus leucas) are present in the lagoon and are known to be involved in attacks on dolphins (Heithaus et al., 2017). Such predation marks have been observed in other Indo-Pacific bottlenose dolphin populations (Heithaus, 2001;Heithaus et al., 2017;Smith et al., 2018;Sprogis et al., 2018b). For instance, across 101 individuals studied in La Réunion Island, 20 showed shark-inflicted bite wounds (Heithaus et al., 2017), leading to an attack rate (19.8%) similar to our study. ...
Article
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Understanding population structure and habitat use of poorly known cetacean species is a first step toward scientifically informed management decisions. In the southern range of New Caledonia (South Pacific), a long-term dataset of Indo-Pacific bottlenose dolphins ( Tursiops aduncus ) encounters primarily during winter seasons 1997 to 2019 (473 group observations) was used to assess social structure, habitat use and potential threats. A total of 338 individuals were photographically identified, forming three distinct communities in the south-west lagoon, the south lagoon and the Isle of Pines. Mark-recapture histories revealed that the three communities were weakly connected and might be considered as independent management units. Suitable habitats were estimated with presence-only distribution models relative to topographic and seabed substrate predictors. Habitat suitability increased with proximity to coasts or reefs, at shallow depth, and over muddy bottom. These habitats had various levels of protection and were used by humans, mostly in the south-west lagoon. External injuries were interpreted to determine natural interactions and potential anthropogenic threats. The prevalence in injuries did not vary among the three areas. A substantial proportion of injuries related to propeller hits was reported, representing a total of 16.7% (34 of 204) of all injuries observed on dolphins. The three communities of Indo-Pacific bottlenose dolphins revealed in the southern part of New Caledonia are particularly vulnerable due to their insularity, their coastal habitat use and the low levels of connectivity found among them. In a context of increasing maritime traffic, fishing and recreational activities, this study provides a useful baseline to the urgent assessment of the conservation status of dolphins in New Caledonia.
... Tooth rakes normally occur along the dorsal ridge and extremities and disappear over time, usually in 5-20 months (Lockyer & Morris, 1990;Scott, Mann, Watson-Capps, Sargeant, & Connor, 2005). Shark bites appear as crescent-shaped wounds and/or deep and widely spaced tooth rakes (Heithaus, 2001) along the dorsal and ventral aspects of the body. ...
... Of potential importance is the spatial distribution of LSM in the IRL, since the condition is found almost exclusively in the northern and central parts of the study area. The dolphin population in the northern IRL has experienced Unusual Mortality Events (UMEs) which occurred in 2001, 2013-2015(NOAA Fisheries, 2019. The causes of the 2001 and 2008 events were undetermined. ...
Article
A previously undescribed skin abnormality, referred to as “linear skin markings” (LSM), has been identified in free‐ranging common bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon, Florida (IRL). The lesions were identified during photo‐identification surveys conducted from 2002 and 2015. LSM presented as distinct, parallel lines running dorso‐ventrally on the torso and varied in length and width. The goals of this study were to determine (1) prevalence of the condition in IRL dolphins, (2) age and sex distribution of affected animals, (3) spatial and temporal distribution patterns, (4) duration of the condition, and (5) development of hypotheses regarding the etiology of the condition. Among 1,357 individual dolphins identified during the study period, 96 (7.0%) showed evidence of LSM. Nearly all (98.8%) cases with an established home range occurred in the northern and central regions of the IRL. The majority of cases of known sex were female (85%), of which 100% had given birth to one or more calves. The mean age of animals with LSM when first observed was 7.3 with a range of 1–20 years. The maximum observed duration of LSM was 15 years. Once observed, the condition persisted indefinitely. The etiology of LSM has not been established.
... Serious injuries to organisms can delay the age at sexual maturity or prevent females from mating while recovering from their wounds (Harris 1989), and catch-induced stress has been suggested as a primary cause of early abortion in elasmobranchs (Adams et al. 2018). Additionally, injuries may also influence the time and frequency of manta rays visiting cleaning stations, as it has been suggested that injured individuals may stay longer at cleaning stations to promote wound healing (Heithaus 2001;Marshall et al. 2011a, b). Therefore, injuries to manta rays can negatively impact an individual's health, their ability to reproduce or their reproductive behaviour, which can directly influence population growth (Le Boeuf et al. 1982;Heithaus 2001) and distribution, as shown in other parts of the world (e.g. ...
... Additionally, injuries may also influence the time and frequency of manta rays visiting cleaning stations, as it has been suggested that injured individuals may stay longer at cleaning stations to promote wound healing (Heithaus 2001;Marshall et al. 2011a, b). Therefore, injuries to manta rays can negatively impact an individual's health, their ability to reproduce or their reproductive behaviour, which can directly influence population growth (Le Boeuf et al. 1982;Heithaus 2001) and distribution, as shown in other parts of the world (e.g. Deakos et al. 2011). ...
Article
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In French Polynesia, both currently recognized manta ray species, Mobula alfredi and M. birostris, are observed. Despite being an important cultural asset and generating significant economic benefits through manta ray watching tourism, published data on the ecology and threats to these species in the region are scarce. Based on an 18-year dataset of sighting records collected by citizen scientists and during two scientific expeditions, this study provides the first insights into the population characteristics and regional distribution of the two manta ray species in French Polynesia. A total of 1347 manta ray photographs (1337 for M. alfredi and 10 for M. birostris) were examined for the period January 2001–December 2017, with photo-identification techniques leading to the successful identification of 317 individual M. alfredi and 10 individual M. birostris throughout the Society, Tuamotu and Marquesas Islands. We provide the first confirmation of sympatric distribution of both species in the Society Islands. Our results highlight strong and long-term site fidelity of M. alfredi individuals to certain aggregation sites (> 9 years for 16 individuals) and reveal some degree of connectivity between populations, with 10 individuals recorded moving between islands located up to 50 km apart. Analysis of photographs of individuals bearing sub-lethal injuries (n = 68) suggests that M. alfredi are more likely to be injured at inhabited islands (Maupiti or Bora Bora; 75% of all injured individuals) than at uninhabited islands, with 75% of injuries related to boat propeller strikes and fishing gear entanglements. Our findings emphasize the need for further research to allow for a comprehensive evaluation of population structure, size and threats to manta rays in this region.
... A number of studies have suggested a preference for shallow, nearshore habitat in several dolphin species (e.g., Pine et al. 2017;Mann et al. 2000;Gibson et al. 2013;Weir et al. 2008;Mann and Watson-Capps 2005), possibly to protect calves from predators, but there are other benefits of shallow habitats, such as more fish for mother and calf, protection from rough seas, or less interaction with conspecific males. Dolphins might generally change their habitat use in response to shark predation pressure (Wells et al. 1987;Heithaus 2001;Heithaus and Dill 2002). Other studies find little evidence for such nearshore preferences among mother-calf groups (e.g., Elwen et al. 2010), but this might be a consequence of large group sizes that mitigate the impact of sharks. ...
... Other studies find little evidence for such nearshore preferences among mother-calf groups (e.g., Elwen et al. 2010), but this might be a consequence of large group sizes that mitigate the impact of sharks. Large sharks (tiger shark Galeocerdo cuvier), white pointer (Carcharodon carcharias), bull sharks (Carcharhinus leucas), and killer whales (Orcinus orca) are the main predators of odontocetes even if odontocetes are not their major prey source (see Heithaus 2001). Cookiecutter shark scars have been observed on beaked and sperm whales (e.g., McSweeney et al. 2007;Best and Photopoulou 2016), but they are not lethal predators. ...
Chapter
Odontocetes are characterized by slow life histories and extensive maternal care, where offspring nurse for years in some species. Among some of the largest toothed whales, the mother and offspring of one or both sexes stay together for a lifetime, forming the basis of strong matrilineal social units and transmission of culture along maternal lines. Mother and calf face a series of challenges from the moment of birth. The newborn must quickly learn to follow and breathe alongside the mother—and wait for her while she dives for food. Within months the calf transitions to infant position for much of the time, although their swimming ability allows them to associate with others in the mother’s network. Because calves can easily become separated from their mothers, an effective communication system is necessary, and signature whistles and pod-specific dialects appear to serve this function. The mother plays a central role in the development of calf social and foraging tactics. Where this has been studied, calves adopt maternal behaviors, including foraging specializations, and share the mother’s network post-weaning. Although difficult to demonstrate “teaching” per se, dolphins are particularly good candidates given their exquisite learning ability and social tolerance. The role of non-mothers is clearly important in calf development, but whether calf interactions with non-mothers constitute “allomothering” remains unclear for most species. What is clear is that group living by cetaceans affords the calf protection from predators and possibly from infanticidal males. The causes of calf mortality are generally not known, as carcasses are rarely retrieved, but disease, predation, poor maternal condition, and anthropogenic causes (pollutants, provisioning, bycatch, boat strikes), and—rarely—infanticide, are all implicated. Weaning occurs when the calf no longer nurses, evident by cessation of infant position swimming. Interbirth intervals are also used as a proxy for weaning, though the calf frequently nurses during the mother’s subsequent pregnancy. Post-weaning, mothers and daughters continue to have preferential bonds, but in killer whales and pilot whales, sons also continue to have a strong relationship with the mother.
... Entanglement in fishing gear is one of four major sources of such scars and wounds, which include completely or partially collapsed dorsal fins, missing dorsal fins, missing flukes, various scar markings, and skin ulcerations (Norman, 2000;Flores, 2002;López et al., 2003;Read et al., 2003;Reeves et al., 2003;Kock et al., 2006). Other sources of scars include teeth marks from inter-/intraspecific interactions (Kato, 1984;Ford, 1986;Luksenburg, 2014), biting wounds from predators such as sharks and killer whales (Orcinus orca) (Corkeron et al., 1987a(Corkeron et al., , 1987bHeithaus, 2001;Luksenburg, 2014), and vessel collisions or propeller strikes (Bloom & Jager, 1994;Wells & Scott, 1997;Visser & Fertl, 2000;Dwyer et al., 2014). ...
... Wounds from propeller strikes often exhibit a series of parallel curved slash marks (Bloom & Jager, 1994), and injuries from inter-/intraspecific or predator interactions are characterized by rake marks made by teeth (Ford & Ford, 1986;Heithaus, 2001;Luksenburg, 2014). Some injuries observed on humpback dolphins in Xiamen and its adjacent waters and reported in the present study, such as having the upper part of the dorsal fin missing (Individual XM30), body scars (Individuals XM12, XM21, and XM48), and scars around the mouth (Individuals XM27 and XM61), are similar to injuries characteristic of entanglement in fishing nets that have previously been observed in bottlenose dolphins (Tursiops truncatus) (Wells et al., 1998;Friedlaender et al., 2001;Luksenburg, 2014), Guiana dolphins (Sotalia guianensis) (Nery et al., 2008), false killer whales (Pseudorca crassidens) (Nitta & Henderson, 1993;Carretta et al., 2003;Baird & Gorgone, 2005;Luksenburg, 2014), and humpback whales (Megaptera novaeangliae) (Robbins & Mattila, 2001), as well as humpback dolphins in Hong Kong waters (Jefferson, 2000), along the western coast of Taiwan (Slooten et al., 2013;Wang et al., 2017) and the coast of Donsak of Thailand (Jutapruet et al., 2015). ...
... However, to what degree female Shark Bay dolphin's social bonding is related to specific cooperative activities remains an open question, and unlike for males (Gerber et al., 2022) social bonds between females have not yet been shown to have any relationship with survival or reproductive success. Social bonding between females likely plays important roles in predator vigilance (Heithaus, 2001), buffering of male harassment (Connor et al., 2006) and opportunities for social learning , but the benefits are likely to vary across environmental niches (Strickland et al., 2021). ...
Article
The quantity and quality of individual social relationships is a fundamental feature of social structure for group-living species. In many species, individuals preferentially associate with close relatives, which can amplify social benefits through inclusive fitness. Reproductive variation, dispersal and other factors may nevertheless impact relative kin availability, especially for species with slow life histories. As such, variation in family size can affect the social integration of the individual. Here, we investigated the effects of family size on female sociality in a population of Indo-Pacific bottlenose dolphins, Tursiops aduncus, in Shark Bay, Australia. This population exhibits high fission–fusion dynamics, with females varying widely in gregariousness and both sexes remaining philopatric, providing females with both matrilineal and nonmatrilineal kin as potential associates. We used genetic relatedness data obtained from a large single nucleotide polymorphism (SNP) panel and a spatially explicit null model to measure females' propensities to form affiliations with both related and unrelated individuals. We found that females had strong social preferences for matrilineal close (first, second and third degree) kin, but also significant preferences for nonmatrilineal close and more distant kin compared to unrelated individuals. Despite these preferences, we found only small effects of kin availability on individual social position. Stronger and more consistent effects were attributable to individual foraging ecology, although much of the variation remains unexplained. Overall, our models suggest that while female dolphins have strong kin preferences, their social connectivity is not determined by family size; rather, individual foraging strategies and high fission–fusion dynamics enable a diverse repertoire of social strategies to coexist within a population.
... Several shark species can inflict half-moon bites on large cetaceans (Heithaus, 2001a), including Bull sharks (Carcharhinus leucas), Tiger sharks (Galeocerdo cuvier), White sharks (Carcharodon carcharias), and Dusky sharks (Carcharhinus obscurus) (Naessig and Lanyon, 2004;Weller, 2009;). All of these occur off the Ceará State coast (Jucá-Queiroz et al., 2008), where the predation event occurred, supporting Leal et al. the notion that the bite marks could have been inflicted by a shark. ...
... Anthropogenic stressors include boat/propeller strikes, cuts due to fishing hooks or entanglement in fishing lines/nets and anchor lines (Deakos et al. 2011;Carpentier et al. 2019). These sub-lethal wounds can have a severe impact on the population growth and distribution (Heithaus 2001, Deakos et al. 2011. Reproductive behaviour can be altered as the injured animal would spend more time and energy recovering, inducing a delayed sexual maturity (Harris 1989), or even causing early abortion in elasmobranch species ). ...
Thesis
Espèce emblématique et néanmoins menacée qui peuple les mers des régions tropicales et subtropicales du monde entier, la raie manta de récif (Mobula alfredi) est bien présente en Nouvelle-Calédonie. La population de l’archipel n’a cependant encore jamais été étudiée et la compréhension de sa biologie, son écologie, sa dynamique des populations et ses mouvements est encore limitée à l’échelle globale. L’acquisition de connaissances de références pourrait jouer un rôle essentiel pour la conservation de l’espèce. Cette thèse tente de décrire la population, sa structure et l’écologie spatiale de raies manta de Nouvelle-Calédonie en utilisant des approches diverses combinant la science participative à la télémétrie satellite et la génomique. Un suivi de cinq ans permettant la collecte de 1741 photo-identifications de raies manta a permis de connaitre les caractéristiques et la distribution de la population, d’estimer son abondance et d’obtenir un premier aperçu de son utilisation de l’espace et des potentielles sources de blessures. L’utilisation de 21 balises satellites a permis d’obtenir des données de déplacements et de comportements de plongées plus. Finalement, le séquençage du génome de 92 échantillons dont 73 provenant de quatre sites en Nouvelle-Calédonie et 19 de deux sites sur la côte Est de l’Australie a permis de révéler l’existence d’une structure génétique à l’échelle régionale et locale. Les résultats présentés dans cette thèse apportent les premières données sur la population de raies manta de récifs en Nouvelle-Calédonie et proposent les mesures et précautions qui devraient être prises pour évaluer et mitiger les possibles perturbations présentes et futures.
... Individuals gain marks (such as nicks or other damage to the dorsal fin) over time. Known sources of marks on dolphins include nonfatal encounters with fishing gear (e.g., Baird & Gorgone, 2005;Baird et al., 2014;Kiszka et al., 2008), collisions with boats (Wells & Scott, 1997), interactions with conspecifics (e.g., MacLeod, 1998;Marley et al., 2013;Scott et al., 2005), and predation attempts by sharks and Orcinus orca (e.g., Corkeron et al., 1987;Gibson, 2006;Heithaus, 2001). ...
... A proportion of scarred individuals of 3.9% is low compared to other studies of small cetaceans. In Shark Bay, Australia, 74.9% of the individual bottlenose dolphins (Tursiops truncatus) assessed for shark bites, show evidence of healed shark bite wounds (Heithaus, 2001). Similarly, Jeremy et al. (2008) found a higher proportion of animals with scars in Indo-Pacific bottlenose dolphins (Tursiops aduncus, 19%) and melon-headed whales (Peponocephala electra, 56.3%) in the Indian Ocean, but that study pooled injuries across human, conspecific, and predator interactions. ...
Article
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Killer whale (Orcinus orca) populations specialize in both prey and prey acquisition tactics around the world and may be a primary evolutionary driver of the habits of small cetaceans. Entanglement in fishing gear is the most significant anthropogenic threat to the survival of cetaceans worldwide. Distinguishing between natural and human-caused sources of mortality and injury is a key task in marine mammal conservation and management. In British Columbia (BC), Canada, mammal-eating killer whales co-occur with Pacific white-sided dolphins (Lagenorhynchus obliquidens). Bycatch mortality rates are unknown here due to lack of systematic fisheries observer coverage. Drawing from more than three decades of first-hand observations of killer whale attacks on Pacific white-sided dolphins, we identify common themes with respect to predatory behavior of killer whales and anti-predatory responses of dolphins. With input from veterinary pathologists, we outline clues to distinguish killer whale rake marks from scars and wounds likely to be caused by fishery interactions. We examined photographs of 415 well-marked Pacific white-side dolphins for evidence of injuries and scars consistent with either killer whale attacks or fishery interactions. In this case study, healed scars from interactions with killer whale predators were ∼8× more common than scars from fishery interactions (3.9 vs. 0.5%), suggesting that predation is a much bigger threat to Pacific white-sided dolphins in the study area than anthropogenic impacts, or that dolphins are much less likely to survive a fishery interaction than a predation attempt. To advance our knowledge on poorly studied species, multiple lines of evidence will be needed.
... Photographs have also been used to monitor the behavior of disease vector species such as the European badger Meles meles, a potential source of bovine tuberculosis (Chen et al. 2019), and to explore interactions of wildlife with human activities, predators, and conspecifics. Images of marine mammals can be used to quantify wounds and scars likely caused by entanglement with fishing gear (Kiszka et al. 2009), vessel collisions (Kraus 1990, Calambokidis 1995, COSEWIC 2002, Langtimm et al. 2004, and/ or intra-/inter-specific social interactions (Heithaus 2001, Kiszka et al. 2009). ...
Article
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Many of the world’s contemporary species of turtle are extinct or threatened with extinction due to habitat loss, increases in anthropogenic sources of mortality, and poaching (illegal collection). The slow life-history strategy of most turtle species magnifies the effects of poaching because the loss of even a few mature individuals can impact population growth. Returning poached turtles to their population of origin, where possible, can mitigate these effects, but identifying the origin of these individuals can be challenging. We hypothesized that spot patterns might allow assignment of Endangered spotted turtles Clemmys guttata to their population of origin. We characterized and compared spot patterns from carapace photographs of 126 individuals from 10 sites. To explore other types of information these photographs might provide, we also documented carapacial scute abnormalities and quantified their association with genetic diversity and latitude. Spot pattern similarity was not higher within populations than among populations and did not accurately differentiate populations. Carapacial scute abnormalities occurred in 82% of turtles and were not correlated with estimates of neutral genetic diversity. Abnormalities were positively correlated with latitude, implicating thermal stress during the early stages of development in the generation of some scute deformities. However, this relationship became non-significant when line (scute seam) abnormalities were excluded from the data, suggesting a different primary cause for the more severe scute deformities. Further research should continue to investigate the drivers of these deformities, as monitoring shifts in the frequency of scute deformities may provide relevant information for conservation and recovery of endangered turtles.
... Regarded as marine sentinels throughout their range (Bossart 2011, Wells et al. 2004, Tursiops truncatus (Montagu) (Common Bottlenose Dolphin) population parameters are thought to be indicative of environmental disturbances at lower trophic levels . Specifically, survival probability estimates for Common Bottlenose Dolphin populations are known to be affected by numerous environmental factors including anthropogenic noise (Tyack 2009), entanglement (Balmer et al 2019b, Wells et al. 2008, predation (Heithaus 2001, Heithaus and Dill 2002, Smith et al 2018, pollution (Balmer et al. 2011(Balmer et al. , 2019aKucklick et al. 2011;Litz et al. 2007;Schwacke et al. 2002), hurricanes , and large events such as the Deepwater Horizon (DWH) oil spill . The continued and persistent monitoring of estimates of dolphin survival probability over time may thus assist managers in identifying and addressing key threats to the marine environment. ...
Article
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Estimating population parameters such as survival and population growth is critical for the monitoring of at-risk populations of marine mammals. We conducted monthly boat-based photo-identification surveys in the Mississippi Sound and eastern Louisiana waters during January 2011-June 2015 to assess the status of the Mississippi Sound, Lake Borgne, and Bay Boudreau Tursiops truncatus (Common Bottlenose Dolphin) stock. Using the resulting mark-recapture data, we estimated the survival and population growth rates using a reverse capture-recapture method. The estimated monthly survival probability over this period of time was 0.969 (95% CI: 0.964-0.974). The final monthly population growth rate was then estimated to be 1.005 (95% CI: 0.998-1.013), which suggests a relatively stable population.
... A Snapshot of Shark Bay Research (1949Research ( -2020 Tiger sharks in Shark Bay were found to inflict up to 74% of scars on non-calves (Heithaus 2001c). Mothers and older calves were observed to exhibit a flight response to a juvenile great white shark swimming into their group (Connor and Heithaus 1996), and responses of a group to a non-lethal shark attack on a dolphin individual has been documented (Gibson 2006). ...
Research
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This literature review and accompanying metadata synthesis describes published work on the marine environment of Shark Bay across various western science disciplines over seven decades. A total of 775 pieces of literature have been included in this document. The accompanying metadata synthesis contains 962 entries. This resource forms part of the Western Australian Marine Science Institution’s (WAMSI) Shark Bay Science Plan and contributes to the regional understanding and knowledge of the Shark Bay marine environment
... Many studies have focused on marine mammal populations, connecting scarring frequency and type to life-history events and possible causes of death and injury (e.g. Corkeron, Morris, & Bryden, 1987;Heithaus, 2001;Hiruki, Gilmartin, Becker, & Stirling, 1993;Kraus, 1990;Laist, Knowlton, Mead, Collet, & Podesta, 2001;Naessig & Lanyon, 2004;Robbins & Mattila, 2004;Rommel et al., 2007). Direct impacts on the physical well-being of whale sharks are not often observed, with predation and boat strikes thought to occur mainly in the open ocean (Lester et al., 2020;Speed et al., 2008). ...
Article
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• Shark‐based tourism continues to be a rapidly growing industry, and thus understanding the impacts of such activities is essential to mitigate the potential negative effects on the target species. The consequences of provisioning on whale sharks (Rhincodon typus) are not fully understood, although changes to the local environment, ecology, behaviour, and site visitation patterns have been highlighted. Here, the scarring patterns of whale sharks were investigated at a provisioning site in Oslob, Cebu, Philippines, as an indicator of the physical impacts of tourism activities on individual sharks. Photographic identification was used to attribute scars to individual animals (n = 152) between March 31, 2012 and January 31, 2015. • Scars were categorized by type and body location, and were compared with non‐provisioned aggregations in Australia, Mozambique, and Seychelles. Oslob whale sharks were more scarred than other studied populations, with 94.7% (n = 144) having at least one scar, and with 90.8% (n = 138) having more than one scar. Scarring incidence was found to be significantly higher in sharks that regularly visited the provisioning site, and analysis of scarring over time in highly resident sharks showed that all individuals gained scars through periods of consistent re‐sightings. A significantly higher incidence of minor scar types was found, most commonly on the dorsal side of the animal, probably resulting from sustained proximity to boats and ropes throughout the provisioning activities. The consequences of interactions with propeller boats were observed, despite a ban on their use in the provisioning site, highlighting the risk to the species beyond the study site. • We recommend the strict enforcement of a minimum distance between boats and sharks, a zero‐contact policy during interactions, the expansion of the provisioning site, and the implementation of a no‐boat‐access zone around the perimeter of the provisioning site to mitigate potential collisions.
... Besides estimates of abundance, estimating proportions of marked individuals in a population may also be important for other purposes. Several studies have investigated how mark prevalence relates to environmental factors, such as predation, fisheries pressure, and aggression (Baird & Gorgone, 2005;Baird et al., 2014;Heithaus, 2001;Kiszka, Pelourdeau, & Ridoux, 2008;Kügler & Orbach, 2014). The methods outlined here also apply to estimating other ratios used to study populations of cetaceans. ...
Article
Mark rate, or the proportion of the population with unique, identifiable marks, must be determined in order to estimate population size from photographic identification data. In this study we address field sampling protocols and estimation methods for robust estimation of mark rate and its uncertainty in cetacean populations. We present two alternatives for estimating the variance of mark rate: (1) a variance estimator for clusters of unequal sizes (SRCS) and (2) a hierarchical Bayesian model (SRCS‐Bayes), and compare them to the simple random sampling (SRS) variance estimator. We tested these variance estimators using a simulation to see how they perform at varying mark rates, number of groups sampled, photos per group, and mean group sizes. The hierarchical Bayesian model outperformed the frequentist variance estimators, with the true mark rate of the population held in its 95% HDI 91.9% of the time (compared with coverage of 79% for the SRS method and 76.3% for the SRCS‐Cochran method). The simulation results suggest that, ideally, mark rate and its precision should be quantified using hierarchical Bayesian modeling, and researchers should attempt to sample as many unique groups as possible to improve accuracy and precision.
... In aquatic mammals, such as cetaceans, spinal defor-mations may further result from traumatic injury, with ship strikes (e.g. Wells & Scott 1997), fisheries interactions (Van Bressem et al. 2007), interspecific aggression or predation (Ross & Wilson 1996, Heithaus 2001 and agonistic behaviour from conspecifics (Watson et al. 2004, Robinson 2014) having all been implicated as causative factors. ...
Article
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Photographs collected during a 23-year photo-identification study in the Moray Firth were examined to assess the prevalence, type and severity of vertebral deformations present in bottlenose dolphin (Tursiops truncatus) calves. Fifteen cases of presenting spinal anomalies (scoliosis, kyphosis, lordosis and combinations thereof) of variable severity were identified in 7.4% of all known calves from the population. 13 of the 15 cases were manifest from birth or acquired from an early age, as ascertained from longitudinal sightings histories of their mothers. Most afflicted calves died during early development or shortly after maternal separation. However, three survived to adulthood and persist in the population to date, in addition to two dependent infants whose fate still remains to be established. At 15+ years of age, the oldest surviving individual was remarkably one of the most severe cases identified, highlighting the ability of these delphinids for adaptation to such gross structural deformities. The aetiology of the observed conditions could be attributed to a range of causative factors that may have implications for the well-being and health of this North Sea coastal dolphin population and merits further investigation.
... Approaches based on photo identification data have the potential to provide important information on population demographic parameters and geographical ranges. Also, the use of underwater photographic evidence to monitor individual body conditions for detection of malnutrition due to poor feeding or occurrence of scarring and wounds indicative of predation risk (Corkeron et al. 1987, Cockcroft et al. 1989, Cockcroft 1991, Bearzi et al. 1997, Heithaus 2001) is recommended. ...
Thesis
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The spinner dolphin (Stenella longirostris) is among the cetacean species most vulnerable to disturbance and sub-lethal effects of dolphin watching. This industry brings tourists in contact with wild populations and can therefore be conceptualised as a complex coupled social-ecological system. The understanding of system functioning and the design of effective schemes for its sustainable management require the investigation of both the ecological and social system components, and their interactions. In the Egyptian Red Sea, a growing dolphin watching industry is currently targeting the spinner dolphin in its resting areas. Behaviour and ecology of the species were analysed at two resting areas exposed to tourism (Samadai and Satayah reefs) and one without tourism (Qubbat’Isa). At all sites, dolphin schools displayed the traditional circadian ecology. School behaviour patterns while in the reef changed as the day progressed and in response to tourism activities. In tourism sites, rest appeared delayed compared to control. The Satayah population of 292 (SE=36.9) long-term resident individuals rarely interacted with the dolphins from Samadai in the study site. No interchange was recorded between Qubbat’Isa and the other two resting areas, thus suggesting that the species is organised in (semi) isolated populations regularly occurring in a given resting area. The populations under investigation displayed consistent responses to anthropogenic pressures. Groups were more often loose and active in presence of tourism disturbance in the morning and midday. In the afternoon, pressures caused Satayah groups to be more often tight and less often active, and had no effects on Samadai groups. The control conditions in the two impacted sites differed from control conditions at the control site, and from spinner dolphin behaviour under control conditions in other locations (e.g. Hawai’i). The investigation of stakeholders’ attitudes, experiences and beliefs revealed a strong sense of stewardship towards these natural resources in the community of users, a promising sign for possible community-based schemes. However, rooted social conflicts, fragmentation and uneven power relationships were also pervasive in the case. Results from Samadai and Satayah indicated that both systems are reaching their carrying capacity. The results of this study suggest that the Satayah population is under serious threat and management interventions should be urgently implemented to safeguard the local populations. It is recommended that the dolphin tourism system be reformed with micro-scale (e.g. creation of cooperatives) and meso and macro scale intervention (e.g. legal reforms, regional certification schemes) to enable conservation to persist. Given the critical conditions at Satayah reef, immediate action should be taken to suspend or drastically reform swim-with dolphin operations on site. Continued research on ecological aspects, as well as behavioural and biological impacts is recommended for the design of adaptive management schemes. A determined effort to involve the social sciences to unravel features and relationships of local actors will enable and encourage decision makers to act on the biological results. This study reasserts the importance to adopt a precautionary principle in the management of dolphin watching operations and emphasises the necessity to implement integrated multi-level and multi-scale management schemes for their sustainability.
... Single or multiple parallel deep cuts, or V-shaped cuts: these types of wounds are most likely to be caused by helix blows (Read & Murray, 2000;Elwen & Leeney, 2010;Byard et al., 2012;Dwyer et al., 2014;Luksenburg, 2014). Deep and unclean wounds: half-moon and spaced tooth marks (Wilkinson et al., 2017) may be the result of shark attacks (Heithaus & Dill, 2002;MacLeod et al., 2007) or fatal interactions between species (Visser et al., 2010), that do not match the natural marks caused by dolphins' interactions (Heithaus, 2001). ...
Article
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This study focuses on the dolphins populating the water between Gibraltar and Algeciras in the south Iberian Peninsula, an area subjected to pressure due to high human activity. The area is considered an important feeding and breeding ground for common dolphins ( Delphinus delphis ). Due to the degree of residence of some specimens, and the large gap in knowledge about the evolution of wounds in D. delphis specimens with lacerations, this work sought to perform the following analyses: identify lacerated individuals; characterize sequences of ‘before – during – after’ with respect to the occurrence of lacerations; and associate the type of injury with its severity. This work will inform future studies by expanding a database on injured individuals and contribute to periodical monitoring of specimens that frequent these geographic areas. Between 2013 and 2017, we were able to track the healing process of five injured individuals of common dolphins from a whale-watching platform thanks to photo identification. The animals exhibited fresh external wounds from different sources. In the majority of individuals, the wound-healing processes lasted 3–21 weeks. The frequency with which sightings are made and knowledge about the local population will help track injured animals, follow their wound evolution, and document their survival rates. The documented injuries inflicted by human interactions described in this paper may include fishing interactions and propeller strikes, probably as a consequence of the high intensity of recreational fishing and whale-watching activities in the area.
... The striped mullet, Mugil cephalus, is considered the mainstay of the bottlenose dolphin diet in the Gulf of Mexico (Blair . Predation by shark is a significant cause of mortality of bottlenose dolphins in various areas around the world (e.g., Australia: Heithaus, 2001; South-eastern United States: Wells et al., 1987). Occasionally they are also predated by killer whales (Gowans et al., 2008). ...
Thesis
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Studies on animal bioacoustics, traditionally relying on non-human primate and songbird models, converge towards the idea that social life appears as the main driving force behind the evolution of complex communication. Comparisons with cetaceans is also particularly interesting from an evolutionary point of view. They are indeed mammals forming complex social bonds, with abilities in acoustic plasticity, but that had to adapt to marine life, making habitat another determining selection force. Their natural habitat constrains sound production, usage and perception but, in the same way, constrains ethological observations making studies of captive cetaceans an important source of knowledge on these animals. Beyond the analysis of acoustic structures, the study of the social contexts in which the different vocalizations are used is essential to the understanding of vocal communication. Compared to primates and birds, the social function of dolphins’ acoustic signals remains largely misunderstood. Moreover, the way cetaceans’ vocal apparatus and auditory system adapted morphoanatomically to an underwater life is unique in the animal kingdom. But their ability to perceive sounds produced in the air remains controversial due to the lack of experimental demonstrations. The objectives of this thesis were, on the one hand, to explore the spontaneous contextual usage of acoustic signals in a captive group of bottlenose dolphins and, on the other hand, to test experimentally underwater and aerial abilities in auditory perception. Our first observational study describes the daily life of our dolphins in captivity, and shows that vocal signalling reflects, at a large scale, the temporal distribution of social and non-social activities in a facility under human control. Our second observational study focuses on the immediate context of emission of the three main acoustic categories previously identified in the dolphins’ vocal repertoire, i.e. whistles, burst-pulses and click trains. We found preferential associations between each vocal category and specific types of social interactions and identified context-dependent patterns of sound combinations. Our third study experimentally tested, under standardized conditions, the response of dolphins to human-made individual sound labels broadcast under and above water. We found that dolphins were able to recognize and to react only to their own label, even when broadcast in the air. Apart from confirming aerial hearing, these findings go in line with studies supporting that dolphins possess a concept of identity. Overall, the results obtained during this thesis suggest that some social signals in the dolphin repertoire can be used to communicate specific information about the behavioural contexts of the individuals involved and that individuals are able to generalize their concept of identity for human-generated signals.
... Compared to shark rakes, conspecific rakes tend to be smaller, shallower, and have fewer lines associated with them. Shark bites tend to have a more circular pattern with deeper and far more teeth marks (Heithaus 2001). Overall, the patterns associated with conspecific scars are distinct from those acquired from heterospecific interactions. ...
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Social living brings competition over mates, relationships, and resources, which can translate to direct conflict. In dolphins, tooth rakes received from conspecifics are highly visible and reliable indicators of conflict. New rakes indicate recent conflicts while healed rakes suggest older instances of conflict. Here, we investigate the healing time of conspecific tooth rakes in wild bottlenose dolphins, create a demographic profile of injury risk in the population, and consider the implications for age- and sex-specific aggression. Using photographic and scarring data from the Shark Bay Dolphin Research Project spanning 31 years (N = 269 tooth rakes), healing time was analyzed using a subset of sequential photographs of the same body part over 1–12 years (N = 70 tooth rakes). Ninety percent of tooth rakes in males and 95% of tooth rakes in females were no longer visible within 400 days, with males taking longer to heal than females. Using the full sample, we examined age and sex-effects on the prevalence of new tooth rakes. A negative quadratic model best fitted tooth rake prevalence patterns from ages 0 to 13 and a positive linear regression best fitted tooth rake prevalence patterns from ages 13 to 30. Both analyses revealed significant age and sex effects, where males had more tooth rakes than females. Age differences in tooth rake prevalence may be attributed to life history events such as sexual maturity onset, male-male competition and alliance formation, and sexual coercion. These results contribute to our understanding of the relationship between social conflict and life history strategies in long-lived mammals. Significance statement In wild dolphins, tooth rake scars indicate conspecific conflict, and the timing of such conflict clarifies the challenges faced during each life history stage. Based on > 30 years of longitudinal data, we created a demographic profile of new tooth rakes to identify patterns of age- and sex-specific received aggression. Males had more tooth rakes than females, but females healed faster than males. Juveniles had the greatest tooth rake prevalence compared to calves and adults, suggesting greater exposure to some level of conflict. Differences in patterns of tooth rake prevalence and aggression have implications regarding the costs of sexual maturity and reproduction in dolphins. To our knowledge, no study has examined the rate of received aggression across the lifespan. Our methods can be applied to other studies of wild marine mammals, where agonistic encounters are difficult to observe, but wounds are apparent.
... Cetacean skin marks have been widely reported [1-3] and revealed a broad spectrum of causes, including infectious diseases (poxvirus and herpesvirus) [4][5][6][7][8][9][10][11][12][13][14][15] as well as environmental causes (solar radiation and water salinity) [16][17][18][19], injuries produced by sharks or parasitic copepods/diatoms, traumatic scarring [16,[20][21][22][23][24][25] and scars caused by propellers [16,17,19,26,27] or fishing gears [13,[28][29][30][31]. Biological and chemical contaminants may contribute to skin mark development in cetaceans [17,19]. ...
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Skin marks occur frequently in many cetacean species across the globe revealing a broad spectrum of causes, including social interactions, infectious diseases and injuries produced by anthropogenic factors. The current study used photo-id data from 2005–2014 to estimate the skin mark pattern on resident bottlenose dolphins (Tursiops truncatus) from the Aeolian Archipelago (Italy). Thirteen skin mark types were identified and their origin, prevalence and permanence time were examined. The pattern of skin marks was assessed for the abundance, richness, distribution and severity in six body regions and compared among age classes, sex and degree of dolphins’ interaction with trammel nets (DIN). Our results showed higher prevalence, abundance, richness and distribution of skin marks in adults than in the younger age classes, with the exception of black marks and white ring lesions. The prevalence and abundance of skin marks were higher in males than females, with the exception of scratches and white patches. Moreover, gunshot wounds, mutilations and irregular dorsal fin edges were found only on adult males. Since males showed higher DIN than females and, in dolphins with higher DIN, skin marks were more abundant and frequently distributed in different body regions, the skin mark pattern in regard to DIN seems to be sex-related. The more severe marks were observed on adults, males and dolphins with higher DIN, namely skin disorder, tooth rake marks, small shallow indentations, deep indentations and mutilations. On the contrary, the severity of scratches, white patches and dark ring lesions was higher in females than males, but not significantly related to DIN and age of the individuals. Our results showed that photo-id data provide an efficient and cost-effective approach to document the occurrence of skin marks in free-ranging bottlenose dolphin populations, a critical step toward understanding the cause and supporting the conservation strategies.
... A third possibility is that heterozygous mothers are better at rearing their calves, which includes protecting them against sharks. Sharks represent a major threat to the survival of calves in SB (Heithaus 2001). A previous study by showed that calving success of the SB female dolphins is driven by a combination of social and genetic interactions. ...
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... Knowlton & Kraus 2001, Robbins & Mattila 2004) and semi-aquatic turtles (Saumure et al. 2007). Similar methods have facilitated estimation of predation rates in a variety of taxa, including cetaceans (Heithaus 2001), fish (Reimchen 1988), invertebrates (Murtaugh 1981, McCallum et al. 1989), rays (Marshall & Bennett 2010), and sea turtles (Heithaus et al. 2002), and have also been used to investigate the relative impact of both natural and anthropogenic threats to cetaceans (Kiszka et al. 2008, Luksenburg 2014, aquatic turtles (Cecala et al. 2009, Bennett & Litzgus 2014, and whale sharks (Speed et al. 2008). It is important to recognize that a key bias inherent in these types of studies is that only individuals surviving injury are sampled. ...
Article
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Identification and understanding of various patterns of injury in marine species such as cetaceans and sea turtles can elucidate corresponding threats and inform conservation efforts. Here we used standardized external injury assessments to investigate the relative importance of direct anthropogenic and natural threats to the Northwest Atlantic population of leatherback turtles Dermochelys coriacea, and to evaluate whether susceptibility to these threats varies between low-latitude nesting and high-latitude foraging regions, and by sex and size (i.e. age). We sampled leatherbacks foraging in temperate waters off Nova Scotia, Canada (n = 92), and at a nesting beach in Trinidad, West Indies (n = 137), where, combined, 62% of turtles exhibited characteristic markings associated with at least 1 injury (i.e. entanglement scarring, amputations, bites, etc.). There were no significant differences in injury rate or type between regions or between sexes or size classes. The proportion of leatherbacks exhibiting injuries of suspected anthropogenic origin (34%) was significantly higher (p < 0.001) than the proportion with injuries of suspected predatory origin (16%), but did not exceed the proportion with injuries of unknown origin (34%). Nineteen percent exhibited injuries indicative of entanglement in rope, lines, or nets, and 17% showed evidence of potential interaction with hooks. These results suggest that the Northwest Atlantic leather back population faces common and possibly widely distributed threats from both predators and fishing gear across its range and are consistent with growing evidence positing fisheries bycatch as one of the principal direct threats facing this species.
... Finally, predation is another major force that can influence social structure (see review in Krause and Ruxton 2002). In the Normano-Breton Gulf, killer whales and shark species were not observed and no shark bites were ever recorded, in contrast to Australian and NWA inshore populations (Wells et al. 1987;Heithaus 2001). This lack of predation could have an important evolutionary impact and might contribute to the possible absence of effect of relatedness on social structure. ...
Article
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Animal social structures are shaped by external environmental factors and individual intrinsic behavioral traits. They represent a balance between the costs and benefits of group-living to maximize individual fitness. Bottlenose dolphin, Tursiops truncatus, societies are fission–fusion with high variations in association strength, grouping patterns and influence of kinship on social bonds throughout the wide range of habitats where they occur. Here, the drivers of social structure in resident coastal bottlenose dolphins of the Normano-Breton Gulf (English Channel) were studied using a multidisciplinary approach combining individual monitoring (photo-identification) information, genetic and ecological data. First, the ecological segregation of the social clusters was tested. Then, the influence of kinship, sex and ecological specializations on association patterns was evaluated. Stable isotopes revealed that the social clusters had relatively distinct ecological niches. Resource partitioning among social clusters may reduce competition and may allow the area to sustain a larger resident bottlenose dolphin population. Individuals did not preferentially associate with related individuals or individuals of the same sex. However, sample size was relatively low for females and, therefore, a role of kinship in shaping association patterns could not be totally ruled out for those individuals. Instead, dolphins preferentially associated with individuals of similar ecology. The study also emphasizes that stable isotope analysis is a promising tool to investigate the link between social structure and ecological specializations, particularly in taxa that are difficult to observe in the wild.
... In Algoa Bay, several bottlenose and humpback dolphins show severe lesions of shark bites on their body, providing evidence that shark attacks on dolphins occur in this area (TB, unpublished data). Other studies showed that bottlenose dolphins in the coastal waters of southern Africa display lower sharkinflicted scar rates (10%-20%, see Cockroft et al. 1989) than other areas, such as Shark Bay (74%), Moreton Bay, Australia (37%), or Sarasota (31%; see Heithaus 2001a). The reduced incidence of shark related injuries may reflect the larger group sizes. ...
Article
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This study investigates how group size of Indo-Pacific bottlenose dolphins (Tursiops aduncus) changes temporally, spatially, and/or with predominant behavior at two discreet sites along the Eastern Cape coastline of South Africa: Algoa Bay and the Wild Coast. The mean group size of bottlenose dolphins was large with an average of 52 animals. Significantly larger groups were observed in Algoa Bay (math formula = 60, range = 1–600) than off the Wild Coast (math formula = 32.9, range = 1–250). In Algoa Bay, the mean group size increased significantly over the study period, from an average 18 animals in 2008 to 76 animals in 2016. Additionally, the largest average and maximum group sizes ever reported both in South Africa and worldwide, were recorded in Algoa Bay (maximum group size = 600). Neither season nor behavior had a significant effect on mean group size at both sites. Similarly environmental variables such as the depth and substrate type also had no influence on group size. It remains unclear which ecological drivers, such as predation risk and food availability, are leading to the large groups observed in this area, and further research on abundance and distribution of both predators and prey is necessary.
... Seasonal residents are individuals that use a specific area for a couple of months or an entire season during con- secutive years (Zolman 2002). This pattern is usually associated with spatiotemporal varia- tion in prey availability (Mead and Potter 1990, Barco et al. 1999, Toth et al. 2011) and / or the presence of predators ( Heithaus 2001, Heithaus andDill 2002). Transient or no- madic residents are animals that show minor or no site fidelity , Zolman 2002. ...
Article
Biotic and abiotic factors determine presence and habitat use pattern of individuals within a population. In this study, presence, behavior, and resighting patterns of transient bottlenose dolphins (Tursiops truncatus) were evaluated in relation to upwelling and downwelling events in a marine reserve in North-Central Chile, between 2005 and 2009. The study period was divided into four phases according to wind direction and intensity: upwelling-favorable (UF), transition I (TI), convergence (Cv) or downwelling, and transition II (TII). Results show that transient bottlenose dolphins are an open population with low resighting rates. Highest occurrence and a largest number of transient dolphins were identified during 2009, probably due to an increase in prey availability. The most frequent behavior observed was traveling, followed by feeding and socializing. Traveling was mainly recorded in individuals seen only once and in years with low productivity. In contrast, feeding was observed in individuals seen two or more times, was similar among phases, and was more frequent in moreproductive years. Social behavior was associated with the highest resighting rates. This study documents how transient bottlenose dolphins use the area based on their resighting patterns and suggests that periods of upwelling and downwelling modulate behavior displayed by these dolphins within the area.
... Risk of tiger shark (Galeocerdo cuvier) attack is high among Shark Bay bottlenose dolphins (Heithaus 2001). Although tiger sharks disproportionately use shallow habitats and are in high abundance in the warmer months (September through May), dolphin habitat use does not differ by sex when sharks are abundant (Heithaus and Dill 2002), indicating that predation does not drive habitat segregation, but social segregation may result from females with calves associating with one another for calf protection Gibson and Mann 2008). ...
Article
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Sexual segregation is widespread in mammals, although the proximate causes are poorly understood in monomorphic species. Indo-Pacific bottlenose dolphins (Tursiops aduncus), which exhibit a high degree of fission–fusion dynamics, offer a useful lens to examine the ecological and social drivers of sexual segregation. While ecological hypotheses suggest that sexual segregation is a by-product of sex-specific ecological preferences (e.g., related to habitat, foraging, or predator avoidance), the social hypothesis proffers that segregation results from same-sex preferences (e.g., due to cooperative benefits) and/or opposite-sex avoidance (e.g., due to competitive or exploitative interactions). Indo-Pacific bottlenose dolphin females range from nearly solitary to highly sociable. Males associate in alliances that cooperate to sequester individual females and exclude competing males. Given evidence for allied sexual coercion, our primary hypothesis was that sexual segregation is driven by female avoidance of aggressive males. However, given robust evidence for sex-biased foraging tactics, ecological factors likely also contribute. Using the Sexual Segregation and Aggregation Statistic with 17,468 sighting records spanning 31 years, we found strong sexual segregation. Unique to our work, we analyzed the direction of joins and leaves between males and females from focal observations (N = 10,715 fission–fusion events, 87 females, 111 males) to determine which sex drives sexual segregation. Females drove segregation by rarely joining and often leaving males. Although ecological factors likely reinforce sexual segregation, social factors predominate. This study demonstrates a sex-bias in fission–fusion dynamics in a socially complex wild mammal population and offers strong empirical support to the social hypothesis of sexual segregation.
... The causes of calf mortality in the Shannon Estuary remain largely unknown. There are no known predators of bottlenose dolphins in Ireland; dolphins are not subjected to predation by sharks as they are in other populations such as in Shark Bay, Australia (Heithaus 2001). Therefore, predation does not seem to account for any calf deaths in the Shannon Estuary. ...
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This study investigates the female reproductive parameters and population demographics of bottlenose dolphins (Tursiops truncatus) in the Shannon Estuary, Ireland, using long-term relational sightings and photographic databases. Data were collected between 2008 and 2016, during 654 boat-based surveys, from two dolphin-watching vessels and a research vessel. During 1018 sightings, 4231 identifications of 184 individual dolphins were recorded. The population size was charted through direct counts of known dolphins from 2011 to 2015 (mean 142, range 131–150), with 145 extant individuals in 2015: 80 adults, 25 juveniles, and 40 calves. Excluding dependent calves, 121 individuals were sighted, of whom 98% (n = 119) were sighted in multiple years, with 64% (n = 77) sighted in all 4 years (2012–2015). Between 2008 and 2016, 37 reproductive females and 69 dependent calves were recorded. Overall, 35% (n = 13) of these females were sighted with one calf, 43% (n = 16) with two calves and 22% (n = 8) with three calves. An average of seven (range 3–10) calves were born each year. Parturition peaked in July. Weaning ages ranged from 2.0 to 4.1 (mean 2.9) years. The mean inter-birth interval ranged between 2.7 ± 0.6 and 3.5 ± 1.3 years, depending on the method used. Mean annual calving rate was 0.29 young-of-year/reproductive female/year. Average crude birth rate was 0.07 ± 0.01. Fecundity was 0.26 ± 0.03. An average 11% of newborn calves were lost before age 1. These results are generally within the lower range of values reported for similar populations and provide essential data for conservation management and global bottlenose dolphin research.
... Sharks are known to attack both young and adult odontocetes, with most reports being in well-studied populations of bottlenose dolphins. In particular the dolphins in Shark Bay, Australia, face a higher rate of predation than other populations, with almost 75% of the study population having shark bite scars (Heithaus 2001). ...
... Calf survival is positively influenced by strong and stable bonds between adult females in primates and bottlenose dolphin societies (Silk et al. 2009, Fr ere et al. 2010a. Predation is unlikely to influence association patterns as no shark bites were ever recorded; this is in contrast to populations exposed to shark attacks (Heithaus 2001). Kin selection (Hamilton 1964) may also play a role in shaping the strong social bonds observed in this community. ...
... Predation is potentially a major factor influencing grouping behaviour in dolphins. Predation risk influences dolphin habitat use and grouping in Shark Bay (Heithaus & Dill, 2002), and 74.2% of dolphins (noncalves) bear shark bite scars (Heithaus, 2001). Because lone individuals are more vulnerable to predators (Alberts & Altmann, 1995;Hirsch & Morrell, 2011), the amount of time young spend alone has implications for predation risk (Hamilton, 1971;Janson & van Schaik, 2002). ...
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Sex differences in adult behaviour are well documented, but less is known about the ontogeny of these differences. In mammals, the transition to independence, from infancy to the juvenile period, is when these sex differences are likely to become prominent. Here, we examined sex differences in behavioural development among calf and juvenile bottlenose dolphins, Tursiops aduncus, from 2 years preweaning to 2 years postweaning and whether these differences were consistent, or not, with three nonmutually exclusive hypotheses regarding the function of the juvenile period: the social skills, protection/safety and energy allocation hypothesis. All hypotheses received some support, but strikingly so for females. First, sex differences in the nature and quality of juvenile social bonds appear to foreshadow adult association patterns. Juveniles had a greater proportion of same-sex associates than calves. Second, although neither sex increased their number of associates from infancy to juvenility, a pattern that might mitigate predation risk, avoidance between juveniles and adult males suggests that both sexes reduce the likelihood of conspecific aggression. This pattern was more marked for juvenile females. Third, females, but not males, increased foraging rates from late infancy to the early juvenile period, even surpassing typical adult female foraging rates. This is likely related to the future energetic demands of maternal investment and skill development required for specialized foraging tactics, which are female biased in this population. This study provides a first step towards understanding the transition into independence for cetaceans, insight into how sex differences develop and a glimpse into the function of the juvenile period.
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Sharks are the primary predator of large immature and mature sea turtles, yet the shark species responsible for both lethal and non-lethal injuries are rarely identified because attacks are infrequently observed. Forensic analysis of bite wounds can be used to accurately assess size and potential shark species, especially when combined with species-specific feeding behavior, geographic distribution, and habitat preference. The objective of this study was to use forensic analysis of bite damage on sea turtles to infer shark size and species. Photographs from thirteen cases of documented shark scavenging ( N = 3) and predation ( N = 10) attempts on sea turtles were retrospectively analyzed, including nesting, free-ranging, and/or dead stranded loggerhead ( Caretta caretta ), green ( Chelonia mydas ), Kemp’s ridley ( Lepidochelys kempii ), and leatherback ( Dermochelys coriacea ) sea turtles in Florida and Alabama, USA from 2010–2020. Mean interdental distance (IDD) and bite circumference (BC) of wound marks on sea turtles strongly suggest that the bite marks were generated by white sharks ( Carcharodon carcharias ) in three cases, tiger sharks ( Galeocerdo cuvier ) in three cases, and bull shark(s) ( Carcharhinus leucas ) in one case. For three cases with less distinct wound patterns, two likely shark species were identified, and thereafter narrowed down to a single species based on bite mark characteristics. Due to indistinct IDD and BC ranges of bite wound patterns, a single shark species was not identified in three cases. Forensic analysis enables more accurate evaluations of which shark species predate and scavenge sea turtles, and is a useful technique for studying the behavioral interactions of sharks and turtles more closely.
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Humpback dolphins (Sousa spp.) are obligate shallow‐water and resident species, and they typically live in fission‐fusion societies composed of small‐sized groups with changeable membership. However, we have scant knowledge of their behavioural ecology, starting with potential factors influencing inter‐population variability of their group sizes. Here, we compiled a new global dataset of humpback dolphin group sizes based on 150 published records. Our data indicated an inter‐specific consistency of group‐living strategy among the four species in the Sousa genus, as these species preferred living in small‐sized groups with a mean size of mostly no more than 10, a minimum size of single individual or small pairs, and a maximum size of several tens or ∼100. In addition, we clearly showed the geographic variations in group sizes of humpback dolphins at a global scale. We found that the geographic variations in humpback dolphin group sizes were primarily associated with the latitude, sea surface temperature, and abundance. To conclude, our findings provide insights into social dynamics and socioecological trade‐offs of humpback dolphins, and helps better understand how these resident animals adapted to their shallow‐water habitats from the perspectives of biogeography and socioecology. This article is protected by copyright. All rights reserved
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Marzanoptera tersillae gen. & sp. nov., a new balaenopterid from the Pliocene of the Piedmont in north-west Italy, is described based on a partial skeleton and compared with other living and fossil baleen whales. Marzanoptera tersillae shares characters, such as the shape of the supraoccipital, glenoid fossa of the squamosal and zygomatic process of the squamosal, with ‘Balaenoptera’ bertae. We used a computed tomography scan to view parts of the skull that were otherwise impossible to observe, such as the periotic. A phylogenetic analysis based on 355 character states scored from 87 taxa revealed a well-resolved hypothesis of relationships for Balaenopteridae and a general phylogenetic hypothesis for chaeomysticetes. The monophyly of all superfamily- and family-rank clades and of crown balaenopterid species was confirmed. In addition, a monophyletic group including most basal thalassotherian taxa was recovered. The mollusc fauna associated with the specimen was autochtonous and constituted a residual fossil assemblage indicative of an environmental context located below the base of the storm wave, characterized by a low-energy hydrodynamic regimen. Many shark teeth have been found in close association or embedded within the bones, suggesting a possible scavenging action by two shark species on the whale carcass.
Article
Marzanoptera tersillae gen. & sp. nov., a new balaenopterid from the Pliocene of the Piedmont in northwest Italy, is described based on a partial skeleton and compared with other living and fossil baleen whales. Marzanoptera tersillae shares characters, such as the shape of the supraoccipital, glenoid fossa of the squamosal and zygomatic process of the squamosal, with 'Balaenoptera' bertae. We used a computed tomography scan to view parts of the skull that were otherwise impossible to observe, such as the periotic. A phylogenetic analysis based on 355 character states scored from 87 taxa revealed a well-resolved hypothesis of relationships for Balaenopteridae and a general phylogenetic hypothesis for chaeomysticetes. The monophyly of all superfamily-and family-rank clades and of crown balaenopterid species was confirmed. In addition, a monophyletic group including most basal thalassotherian taxa was recovered. The mollusc fauna associated with the specimen was autochtonous and constituted a residual fossil assemblage indicative of an environmental context located below the base of the storm wave, characterized by a low-energy hydrodynamic regimen. Many shark teeth have been found in close association or embedded within the bones, suggesting a possible scavenging action by two shark species on the whale carcass. ADDITIONAL KEYWORDS: Balaenopteridae-phylogeny-taphonomy-whale falls.
Article
40 years ago, the “life‐dinner principle” was proposed as an example of an asymmetry that may lead prey species to experience stronger selection than their predators, thus accounting for the high frequency with which prey escape alive from interaction with a predator. This principle remains an influential concept in the scientific literature, despite several works suggesting that the concept relies on many under‐appreciated assumptions and does not apply as generally as was initially proposed. Here, we present a novel model describing a very different asymmetry to that proposed in the life‐dinner principle, but one that could apply broadly. We argue that asymmetries between the relative costs and benefits to predators and prey of selecting a risky behaviour during an extended predator‐prey encounter could lead to an enhanced likelihood of escape for the prey. Any resulting advantage to prey depends upon there being a behaviour or choice that introduces some inherent danger to both predator and prey if they adopt it, but which if the prey adopts the predator must match in order to have a chance of successful predation. We suggest that the circumstances indicated by our model could apply broadly across diverse taxa, including both risky spatial or behavioural choices.
Chapter
Animal behaviors are governed by the intrinsic need to survive and reproduce. Even when sophisticated predators and prey are involved, these tenets of behavioral ecology hold. Similar to humans, fear can be a strong motivator for change in animals. The terrestrial ecology literature is replete with examples of fear-mediated behavioral effects on species and community networks. In contrast, the marine mammal literature is sparse in its recognition and consideration of nonconsumptive effects or risk effects arising from powerful and lethal predators, such as killer whales and large sharks. This chapter encapsulates the ecology of fear concept by providing representative examples from the marine mammal literature with consideration of prey and predator perspectives. Additionally, research data gaps and new avenues for scientific examination are highlighted within documented examples. Lastly, conservation practitioners and marine mammal scientists are encouraged to adapt theoretical concepts and methods from predation risk studies to better understand the effects of nonbiological stressors on marine mammal species.
Chapter
The behavioral ecology of Tursiops aduncus (Indo-Pacific bottlenose dolphin) is usually reviewed alongside the much more widely studied T. truncatus (common bottlenose dolphin). However, the smaller, typically shallow water T. aduncus has been closely scrutinized in Australian and Japanese waters. As a result, there now exists a robust body of information spanning all three of Hinde’s levels of social analysis—interactions, relationships, and social structure—that may be unmatched in any other cetacean. Research on T. aduncus has contributed significantly to the social complexity hypothesis of large brain evolution and our understanding of delphinid mating systems, communication, and individual differences in foraging tactics within populations. Here, we focus on behavioral research at two primary sites, Shark Bay in Australia and Mikura Island in Japan, with additional observations of importance from other locales in each region.
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Long-term studies often rely on natural markings for individual identification across time. The primary method for identification in small cetaceans relies on dorsal fin shape, scars, and other natural markings. However, dorsal fin markings can vary substantially over time and the dorsal fin can become unrecognizable after an encounter with a boat or shark. Although dorsal fins have the advantage in that they always break the water surface when the cetacean breathes, other physical features, such as body scars and pigmentation patterns can supplement. The goal of this study was to explore the use of dorso-lateral pigment patterns to identify wild bottlenose dolphins. We employed photographic pigment matching tests to determine if pigmentation patterns showed (1) longitudinal consistency and (2) bilateral symmetry using a 30 yr photographic database of bottlenose dolphins (Tursiops aduncus). We compared experienced dolphin researchers and inexperienced undergraduate student subjects in their ability to accurately match images. Both experienced and inexperienced subjects correctly matched dolphin individuals at a rate significantly above chance, even though they only had 10 s to make the match. These results demonstrate that pigment patterns can be used to reliably identify individual wild bottlenose dolphins, and likely other small cetacean species at other sites.
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The incidence of shark induced scars on Indian Ocean bottlenose dolphins caught in gill nets off Natal, on the south-east coast of southern Africa, was monitored between January 1983 and June 1987. The occurrence of dolphin remains in sharks caught in these nets between January 1980 and December 1985 was also recorded. Of the dolphins caught, 10,3% exhibited scars or wounds consistent with shark bites. Only 1,2% of over 6000 sharks caught contained cetacean remains. Four species of shark, the Zambesi (Carcharhinus leucas), the tiger (Galeocerdo cuvieri), the great white (Carcharodon carcharías) and the dusky shark (Carcharhinus obscurvs) were implicated as dolphin predators. Estimates from the number of these four species caught annually and the frequency of occurrence of dolphin flukes and vertebrae in their stomachs suggest that a mininum of 20 bottlenose dolphins or 2,2% of the estimated population in southern Natal coastal waters are killed each year by sharks.Die voorkoms van littekens veroorsaak deur haaie op Indiese Oseaan-stompneusdolfyne wat gevang is in kiefnette in Natal, aan die suidoos kus van suidelike Afrika, is tussen Januarie 1983 en Junie 1987 aangeteken. Die voorkoms van dolfynoorblyfsels in haaie gevang in hierdie nette tussen Januarie 1980 en Desember 1985 is ook aangeteken. Van die dolfyne wat gevang is het 10,3% littekens of wonde vertoon wat ooreenstem met haaibyte. Siegs 1,2% van oor die 6000 haaie wat gevang is het oorblyfsels van Cetacea bevat. Vier spesies van haaie, die bulhaai (Carcharhinus leucas), die tierhaai (Galeocerdo cuvier), die witdoodshaai (Carcharodon carcharías) en die donkerhaai (Carcharhinus obscurus) is aangedui as roofdiere van dolfyne. Skattings van die getalle van die vier spesies wat jaarliks gevang word en die frekwensie van aanwesigheid van dolfynvinne en rugwerwels in die mae dui daarop dat ’n minimum van 20 stompneusdolfyne of 2,2% van die geskatte bevolking in suidelike Natalse kuswaters jaarliks deur haaie doodgemaak word.
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Patterns of association among bottlenose dolphins resident in Shark Bay, Western Australia were analyzed using party membership data. Parties contained an average of 4.8 individuals, but party size and composition were unstable. While these temporary parties often contained both males and females, long term consistent associations generally were between members of the same sex. The highest association coefficients, resulting from very frequent co-occurrence within parties were between males and between mothers and offspring. Males formed subgroups of two or three individuals who consistently associated with each other, and these were stable over periods of at least seven years in some cases. Male subgroups preferentially associated with particular other male subgroups. Females associated most consistently with other females, although not to the same extent as some males. Female associations were better described as a network rather than discrete subgroups. Male-female associations were generally inconsistent and depended in part on female reproductive state. Mothers and their offspring associated very consistently for at least 4 years.
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A description of the social structure of a species is a first step toward understanding its social organization and, ultimately, the evolutionary processes that shaped its social system. Since the mid-1960s the rapid accumulation of information from field studies of terrestrial mammals has made it possible to propose models to explain the evolution of mammalian social systems. These models have examined the species distribution of characteristics such as group size, group compositions, spatial patterns of individuals, and social interactions in relation to environmental variables (for example, Crook and Gartlan, 1966; Eisenberg et al., 1972; Clutton-Brock, 1974; Jarman, 1974; Emlen and Oring, 1977; Wrangham, 1980). Predictable patterns of organization have been found which provide insights into the adaptive significance of the social systems. Until recently, available information for cetaceans has been inadequate to allow construction of comparable models. A surge of systematic field studies of the behavior and ecology of cetaceans is beginning to provide the requisite information for examination of cetacean societies within a general mammalian context. To this end, this chapter presents the results of one study of the social structure of the bottlenose dolphin, Tursiops truncatus.
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A bottlenose dolphin community was studied from small inflatable craft from 1987 to 1994 in a relatively large area (about 800 km2) east of the islands of Loˇsinj and Cres, northern Adriatic Sea. A total of 106 individuals were photoidentified based on natural permanent marks on their dorsal fins. Most of the dolphins were resighted on a regular basis, indicating a high level of year-round site fidelity, although their range was evidently greater than the chosen study area. Dolphin density was highly variable and considerably lower than for most well-known bottlenose dolphin communities. Groups averaged seven individuals, with a mode of two. Groups entirely composed of adults were the smallest, groups with calves the largest. Group fluidity was high, seasonal and yearly changes in mean group size being also considerable. Summer was the peak calving season, with a striking variation in the number of births on alternate years. Poor evidence of shark predation was found. The social organization of this dolphin community seemed to be highly flexible, possibly as an adaptation to cope with environmental changes as well as with a limited and variable availability of prey.
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In Shark Bay, Western Australia, male bottlenose dolphins (Tursiops sp.) cooperate in pairs and triplets to sequester and control the movements of females. We refer to this behavior as "herding" and to the male pairs and triplets as alliances. During a 25-month study (1987-1989) on the social relationships of males, we documented herding in 10 alliances. Males preferentially herded nonpregnant females likely to be in estrus. Alliance members associated with one another consistently when not herding females. Each alliance associated preferentially with one or two other alliances. Occasionally, two alliances combined and took females from another alliance or defended females against such efforts. This study documents multiple-level male alliances within a social group outside of humans.
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Stomach contents from tiger sharks, Galeocerdo cuvier, caught on lines off the central coast of Western Australia were analysed to investigate variations in the diet due to sex, size and geographic location. Stomachs from 84 specimens contained food, while 26 had empty stomachs and 66 had regurgitated. Twelve prey groups were identified, the most common being turtles, sea snakes, teleost fishes, dugongs and sea birds. Dietary overlap was high between males and females. An ontogenetic shift was observed in the diet. Smaller prey (e.g. cephalopods, teleosts and sea snakes) were more common in small individuals, while the occurrence of larger prey (e.g. turtles, dugongs and elasmobranchs) increased with increasing shark size. Differences in the diet were observed between four regions along the central Western Australian coast. The ability to catch and consume large prey, prey availability, prey density, and prey profitability were identified as factors influencing the diet. The high level of occurrence of dugongs and turtles in the diet of G. cuvier, relative to their abundance, suggests that shark predation may play an important role in regulating populations of these species.
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Evidence is presented that bites inflicted by the small squaloid shark, Zsistius brasiliegasis (Quoy and Gaimard), are the causes of crater wounds, crescentic wounds, and related scars on large pelagic fishes and cetaceans. This evidence consists of a crescentic "wound" experimentally produced on the side of a dead fish by a living Isistiis; specialized morphology of the shark's basihyoid cartilage and coracohyoideus muscles, lips, labial cartilages, and spiracles, that, together, enable the shark to form an oral vacuum on a srhooth surface; an experiment in which a living is is ti^^ formed such a vacuum; specialized morphology and arrangement of the mandibular teeth ; close agreement between the range of reported wound widths and the estimated range of bite widths of Isiqtius; agreement between the geographical ranges of Isistius and those fishes and cetaceans which bear crater wounds; and, finally, the presence in Isistius stomachs of hemispheroidal plugs of fish flesh. Speculation on the circumstances that may enable a small, slow shark to make contact with large, swift fishes and cetaceans is included. Isistius apparently qualifies as a temporary parasite. Probably the earliest account of the existence of small, round or oval, scooped-out wounds on the sides of large pelagic fishes is contained in an ancient legend of Samoa (A. Utu, personal communication), which states that atu (skip- jack tuna, Euthynnus pelamis (Linnaeus) ) en- tered Palauli Bay, and, upon approaching the beach, left small round pieces of their flesh as gifts to Tautunu, chief of that community. Evi- dence of this sacrifice was found by the people who caught the atu and observed fresh, round wounds on their sides. This legend provides one of many explanations that have been advanced regarding the causes of such wounds on large pelagic fishes as well as on whales and porpoises. This paper presents evidence that many crater wounds, crescentic wounds, and the resulting scars on pelagic fishes (Figure 1) , and open pit wounds and resulting scars on cetaceans are the results of bites in- flicted by the small squaloid shark, Isistius bra- siliensis (Quoy and Gaimard) . (A second spe- cies, Isistius pliitodus, was described by Garrick and Springer (1964) from the Gulf of Mexico. Although nothing is known of the behavior of
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Contents: Food Related Activity; Reproduction and Growth; Social Integration and Communication; Learning, Protective Behavior; and Responses to Environmental Cycles.
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It is quite common to find several levels of nested male alliances in human political organization¹, ² but these are extremely rare in other species³. Yet we found that male bottlenose dolphins (Tursiops sp.) at Shark Bay, Western Australia, form two levels of alliance within a social network of more than 400 individuals. Fourteen of the males formed highly labile alliances, rather than the more typical stable ones, and joined forces in a large 'superalliance' that competed directly with smaller teams of stable alliances.
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Twenty-four out of 240 fishes caught by bottom lines at 366–3333 m had something in their stomachs. Stomach contents included parts of cephalopods, fish, cetaceans and bottom-living invertebrates, thin rubber sheet and terrestrial mammal bones. The material provides evidence that four species of cephalopod are at least partially demersal and suggests a means by which the tapeworm Phyllobothrium could pass from its secondary to its primary host. During the five biological cruises of R.R.S. ‘Discovery’ between 1967 and 1971 a total of 31 bottom lines with 1483 hooks were fished in depths of water between 366 and 3333 m. The stomachs of the 240 fish caught were examined and 216 (90%) proved to be empty. The high incidence of empty stomachs is thought to be due to frequent loss of food during the ascent from great depths and accounts for our poor knowledge of the feeding habits of demersal fish living at depths exceeding 400 m. The present collection of food from 25 stomachs (24 from ‘Discovery’ collections and one from a fish caught by Mr G. R. Forster from R. V. ‘Sarsia’) of fish belonging to 11 species (Table 1) probably gives little indication of the usual diet of the fish concerned, but its nature prompts some useful speculation and the rarity of such observations justifies placing them on record (Bigelow & Schroeder, 1948; Marshall, 1954). All the fish were caught on lines which lay on the bottom for several hours and it is our firm belief that they were hooked while on or very near the bottom.
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The importance of interactions between sharks and cetaceans has been a subject of much conjecture, but few studies have addressed these interactions. Sharks (order Selachii) have been hypothesized to be important predators on dolphins and porpoises (suborder Odontoceti). Unfortunately, there are often few data to back up claims that certain shark species are major threats to cetaceans. To help identify potential shark predators in speci®c locations, available data on interactions with odontocetes for all shark species that may include cetaceans in their diet are reviewed. Shark species are categorized into groups based on predatory interactions with dolphins and porpoises (regular predators, occasional predators, potential predators, ectoparasites and insuf®cient data). Several shark species that have been overlooked in the cetacean literature are identi®ed as potentially important predators while others that have been suspected to be important predators are probably at most occasional predators. How shark predation can in¯uence dolphin populations, habitat use, group size and behaviour is discussed. How risk of shark predation can vary with habitat attributes in both nearshore and pelagic waters is also discussed. Predator±prey interactions have been the focus of most studies of shark±dolphin interaction, but competitive interactions may also occur. The ®rst analysis of shark±dolphin dietary overlap is presented, which shows it to be signi®cant between common dolphins and several species of sharks, including species that prey upon these dolphins.
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Tiger sharks, Galeocerdo cuvier, are apex predators in a variety of nearshore ecosystems throughout the world. This study investigates the biology of tiger sharks in the shallow seagrass ecosystem of Shark Bay, Western Australia. Tiger sharks (n = 252) were the most commonly caught species (94%) compared to other large sharks. Tiger sharks ranged from 148–407cm TL. The overall sex ratio was biased towards females (1.8:1), but the sex ratio of mature animals (> 300cm TL) did not differ from 1:1. Contrary to previous accounts, tiger sharks were caught more often in all habitats during daylight hours than at night. Tiger shark catch rates were highly correlated with water temperature and were highest when water temperatures were above 19C. The seasonal abundance of tiger sharks is correlated to both water temperature and the occurrence of their main prey: sea snakes and dugongs, Dugong dugon. Stomach contents analysis indicated that sea turtles and smaller elasmobranchs were also common prey. The importance of major seagrass grazers (dugongs and green sea turtles, Chelonia mydas) in the diet of tiger sharks suggests the possibility that these sharks are keystone predators in this ecosystem.
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The sharks and chimaeroids are important members of the deep-water associations of fish of the continental slopes, but little is known about their trophic interactions. The diets of these fish were studied through the deployment of demersal trawls at successive 250 m depth intervals, within a total range of depth of 500 to 2 900 m, in the Rockall Trough to the west of Scotland and Ireland during the period 1975 to 1981. The sharks and chimaeroids, however, only occurred between 500 and 2000 m but principally in the 500 to 1 250 m bathymetric zones. These are the zones of maximum biomass of prey species of fish and probably also of prey species of epibenthos. The sharks divide into 3 trophic groups. Apristurus spp., Centroscymnus crepidater, Ttmopterus spinax and E. princeps exploit micronekton in the vicinity of the sea bed. Centroscyllium fabricii, Centroscymnus coelolepis, Deania calceus and Lepidorhinus squamosus are principally fish eaters. A third group may consist of 2 rarer species in the Rockall Trough, Galeus melastomus and G. murinus that exploit the epibenthos but also, to some extent, the micronekton. The 3 species of chimaeroids (Chimaera monstrosa, Hydrolagus mirabilis and Harriotta raleighana) prey on the epibenthos and the last species may also utilize, to some extent, infaunal species.
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"Part review, part testament to extraordinary dedication, and part call to get involved, Cetacean Societies highlights the achievements of behavioral ecologists inspired by the challenges of cetaceans and committed to the exploration of a new world."—from the preface by Richard Wrangham Long-lived, slow to reproduce, and often hidden beneath the water's surface, whales and dolphins (cetaceans) have remained elusive subjects for scientific study even though they have fascinated humans for centuries. Until recently, much of what we knew about cetaceans came from commercial sources such as whalers and trainers for dolphin acts. Innovative research methods and persistent efforts, however, have begun to penetrate the depths to reveal tantalizing glimpses of the lives of these mammals in their natural habitats. Cetacean Societies presents the first comprehensive synthesis and review of these new studies. Groups of chapters focus on the history of cetacean behavioral research and methodology; state-of-the-art reviews of information on four of the most-studied species: bottlenose dolphins, killer whales, sperm whales, and humpback whales; and summaries of major topics, including group living, male and female reproductive strategies, communication, and conservation drawn from comparative research on a wide range of species. Written by some of the world's leading cetacean scientists, this landmark volume will benefit not just students of cetology but also researchers in other areas of behavioral and conservation ecology as well as anyone with a serious interest in the world of whales and dolphins. Contributors are Robin Baird, Phillip Clapham, Jenny Christal, Richard Connor, Janet Mann, Andrew Read, Randall Reeves, Amy Samuels, Peter Tyack, Linda Weilgart, Hal Whitehead, Randall S. Wells, and Richard Wrangham.
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