The photographic identification (photo‐ID) of individual animals can be time‐consuming and erroneous. Recent efforts to collect photographs of leopard seals (Hydrurga leptonyx) from across their ...range have necessitated the technological streamlining of photo‐ID. We constructed a dataset containing 595 photographs of the head and body of individuals recorded in New Zealand between 2008 and 2022 to test the performance of semiautomated 3 photo‐ID programs: HotSpotter, Interactive Individual Identification System's Pattern+ (I3S), and Wild‐ID. We classified attributes of photographs (e.g., quality) and individuals (i.e., pelage patterns) to assess their effect on performance. We compared performance using Top20 and Top1 Accuracy, defined as the proportion of test photographs where the highest ranked correct identity was in the top 20 and top 1, respectively, matched reference photographs. HotSpotter outperformed I3S and Wild‐ID in both Top20 and Top1 Accuracy of most assessed attributes. Maximizing HotSpotter's performance may be achieved through several methods, including increasing the number and variety of photographs of individuals in the dataset. HotSpotter will likely perform better with photographs without obstructions (e.g., debris from beaches), such as on the pack ice of their primary Antarctic range. We highlight the viability of HotSpotter in assisting the photo‐ID of leopard seals, and more broadly, other species with similar markings.
The movement and distribution of leopard seals in relation to climate change can be examined in a more timely and cost‐effective manner using technology. We evaluated the performance of three semiautomated photographic identification programs, HotSpotter, Interactive Individual Identification System's Pattern+ (I3S), and Wild‐ID, with leopard seal photographs. Attributes of photographs and individuals were assessed to determine program performance with other datasets.
The known distribution of manta rays in Australian waters is patchy, with records primarily centred around tourism hotspots. We collated 11,614 records of Mobula alfredi from photo‐ID databases (n = ...10,715), aerial surveys (n = 378) and online reports (n = 521). The study confirms an uninterrupted coastal distribution from north of 26°S and 31°S on the west and east coasts, respectively. More southerly M. alfredi records relate to warm‐water events with a southernmost extent at 34°S. Coastal sightings of Mobula birostris were rare (n = 32), likely reflecting a preference for offshore waters, but encompass a wider latitudinal extent than M. alfredi of 10–40°S.
The largest known reef manta ray (Mobula alfredi) population in Africa has been monitored for more than 20 years at several locations on the coast of the Inhambane Province in southern Mozambique. ...Nonetheless, before this study, little had been reported on the population dynamics of M. alfredi from Závora, a remote bay in the region. Photographic mark‐recapture was used to investigate the size and structure of M. alfredi that aggregate at “Red Sands,” a reef cleaning station in Závora Bay. An 11 year photographic data set was used to identify 583 M. alfredi individuals between 2010 and 2021. More than half of M. alfredi individuals were resighted at least once, with most encounters (up to 18 for one individual) occurring during the peak sighting period in July–November each year. An even sex ratio was observed, 44% females and 50% males, with no significant difference in resightings between the sexes. Pollock's robust design population models were used to estimate annual abundance, emigration, annual apparent survival and capture probability at Red Sands from July to November over a 6 year period (2016–2021). Abundance estimates varied year to year, ranging from 35 (95% c.i. 30, 45) up to 233 (95% c.i. 224, 249) M. alfredi individuals. Given the seasonal affinity of M. alfredi observed at Red Sands, this study highlights the importance of understanding fine‐scale site use within the larger home range of this population to develop local management strategies.
Wild animals are increasingly exposed to human‐induced threats in the ocean realm. Cetacean species, as predators and biomonitoring models, are subjected to a variety of stressors that may result in ...poor health, injuries, and persistent marks. These malformations can easily be documented by photography or video and can be used to infer about the animals' health, especially if combined with long‐term photographic identification. However, the value of such information for monitoring is vastly increased if a standardised language is used. We provide a broad definition of deformity, as a general concept for conditions or abnormal features in cetacean species, and categorise externally detected deformities in free‐ranging individuals.
We define six categories and 58 sub‐categories of deformities in cetaceans: anatomical malformations (11 sub‐categories), skin lesions (29), anomalous pigmentation (4), injuries due to physical impacts (14), emaciation, and epibionts.
Categorisation was based on peer‐reviewed literature published between 2000 and 2021 (n = 253 studies), comprising 80 of the 101 extant species, documented in studies conducted across 50 countries; reviewed literature included papers from 86 scientific journals, with three journals contributing 100 out of the 253 documents.
Overall, and for both Odontoceti and Mysticeti, physical impact was the most reported category; injuries due to physical impacts were documented in 74% of the 253 studies we reviewed. This may be related to the common exposure of cetaceans to intense human marine traffic and fishing activities.
Especially with the growing use of open science, a consistent and common language is fundamental for data comparison and to support cetacean research, management and conservation efficiently. We suggest that researchers adopt these definitions and categories when describing abnormalities observed in free‐living cetaceans.
Cetacean species, as predators and biomonitoring models, are subjected to a variety of stressors that may result in poor health, injuries, and persistent marks. These malformations can be used to infer about animals' health, especially if combined with long‐term photographic identification. The main goal of this study was to provide: a broad definition of cetacean conditions or abnormal features, generally conceptualised as deformities; a categorisation of externally detected deformities in free‐ranging individuals; and a framework on how and what should ideally be documented to facilitate comparative studies and other research. We have defined six categories and 58 sub‐categories of deformities: anatomical malformations (11 sub‐categories), skin lesions (29), anomalous pigmentation (4), injuries due to physical impacts (14), emaciation, and epibionts. For both Odontoceti and Mysticeti, physical impact was the most reported category, with associated injuries documented in 74% of the 253 studies reviewed. This may be related to the common exposure of cetaceans to intense human marine traffic and fishing activities. Assessing and reporting cetacean deformities through a common language is proposed as a valuable non‐invasive monitoring methodology, which can be implemented alongside, and in support of, photo‐ID studies, and provide crucial indicators of populations and ecosystem health.
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.
The Atlantic nurse shark, Ginglymostoma cirratum, was recently listed as Vulnerable by IUCN Red List, however, as highlighted, little is known about its populations in the Southwestern Atlantic. ...Therefore, population studies are essential to propose status evaluations and new conservation measures.
Natural marks present on the animals' bodies are used as an alternative non‐invasive method rather than the usual tagging system for individual identification, thus avoiding the need for animal handling.
This study aimed to evaluate the population size trend of G. cirratum at the Rocas Atoll Marine Biological Reserve, the only atoll located in the South Atlantic.
Data were collected through underwater filming, photo‐identification, and visual censuses. Three expeditions were carried out in 2018 and the abundance of sharks was sampled in the inner part of Rocas Atoll Marine Biological Reserve.
Sharks were identified individually with the aid of the software Interactive Identification System – Contour (I3S). Based on the re‐sightings of identified animals, two capture–recapture estimators of population size were used (Petersen–Bailey; Jolly–Seber). The estimates were then compared to the only previous estimate made 20 years before, which employed the same number of expeditions and estimators.
A total of 139 sharks were identified from 444 sightings in 63 h of diving effort. Population estimates varied from 200 to 205 sharks, which are significantly lower than the previous estimate (339–368 sharks) made 20 years ago, suggesting a demographic decline in Southwestern Atlantic populations.
Population studies and movement of G. cirratum are essential to inform the implementation of additional protective measures, including the establishment of protected corridors between marine protected areas and the recovery of G. cirratum populations. It is crucial to consider that the distribution of individuals may extend beyond the borders of the non‐take marine protected area. Therefore, the observed decline in the local population could potential indicate a broader decline across the Southwestern Atlantic.
Understanding the survival and reproductive rates of a population is critical to determining its long‐term dynamics and viability. Mark‐resight models are often used to estimate these demographic ...rates, but estimation of survival and reproductive rates is challenging, especially for wide‐ranging, patchily distributed, or cryptic species. In particular, existing mark‐resight models cannot accommodate data from populations in which offspring remain with parents for multiple years, are not always detected, and cannot be aged with certainty.
Here we describe a Bayesian multievent mark‐resight modelling framework that uses all available adult and adult‐offspring sightings (including sightings with older offspring of uncertain age) to estimate reproductive rates and survival rates of adults and juveniles. We extend existing multievent mark‐resight models that typically only incorporate adult breeding state uncertainty by additionally accounting for age uncertainty in unmarked offspring and uncertainty in the duration of the mother‐offspring association. We describe our model in general terms and with a simple illustrative example, then apply it in a more complex empirical setting using 13 years of photo‐ID data from a critically endangered population of beluga whales Delphinapterus leucas. We evaluated model performance using simulated data under a range of sample sizes, and adult and offspring detection rates.
Applying our model to the beluga data yielded precise estimates for all demographic rates of interest (despite substantial uncertainty in calf ages), including nonbreeder survival and reproductive rates lower than in other beluga populations. Simulations suggested our model yields asymptotically unbiased parameter estimates with good precision and low bias even with moderate sample sizes and detection rates.
This work represents an important new development in multievent mark‐resight modelling, allowing estimation of reproductive and juvenile survival rates for populations with extended adult—offspring associations and uncertain offspring ages (e.g. some marine mammals, elephants, bears, great apes, bats and birds). Our model facilitated estimation of robust demographic rates for an endangered beluga population that were previously inestimable (e.g. nonbreeder and juvenile survival, reproductive rate) and that will yield new insights into this population's continued decline.
The endangered population of humpback whales (Megaptera novaeangliae) breeding and calving off the Cape Verde Islands (CVI) are known to migrate to feeding areas located along the eastern margin of ...the North Atlantic Ocean (Iceland, and Norway). Here, we report for the first time a confirmed migration of an individual humpback whale from CVI breeding ground to a western North Atlantic feeding ground of West Greenland. This individual humpback, which was photographed and identified off the coast of West Greenland in 2021, was previously documented in CVI 22 years before (1999). An annual subsistence hunt for humpbacks occurs in West Greenland and the resighting at this location with a humpback whale from CVI has strong implications for the conservation efforts of the small CVI population.
The endangered population of humpback whales (Megaptera novaeangliae) breeding and calving off the Cape Verde Islands (CVI) are known to migrate to feeding areas located along the eastern margin of the North Atlantic Ocean (Iceland and Norway). Here, we report for the first time the confirmed migration of an individual humpback whale from CVI breeding ground to a western North Atlantic feeding ground, West Greenland. This individual humpback, which was photographed and identified off the coast of West Greenland in 2021, was previously documented in CVI 22 years before (1999). An annual subsistence hunt for humpbacks occurs in West Greenland, and the resighting at this location with a humpback whale from CVI has strong implications for the conservation efforts of the small CVI population.
Fluctuations in aggressive behavior of group‐living species can reflect social conflict and competition for resources faced by individuals throughout their lifespan and can negatively impact survival ...and reproduction. In marine mammals, where social interactions are difficult to observe, tooth rake marks can be used as an indicator of received aggression. Using 38 years of photographic data, we quantified the occurrence of tooth rake marks on wild resident killer whales (Orcinus orca), examining the effects of age, sex, and prey abundance on rake density. Our analysis revealed sex and age effects, with males exhibiting higher rake density than females and rake density declining significantly with age. Contrary to predictions, we observed an increase in rake density across the population as the abundance of their primary food resource, Chinook salmon (Oncorhynchus tshawytscha), increased. These results provide indirect evidence of fluctuations in received aggression from conspecifics across the lifespan of an individual, possibly reflecting changes in patterns of social conflict which may be mediated by resource abundance. Our findings highlight the need for further research to examine the fitness consequences of aggression in killer whales and to understand the proximate mechanisms by which resource abundance influences rates of aggression in the population.
1.Cook Inlet beluga whales (CIBWs; Delphinapterus leucas), are an isolated and declining endangered population in Alaska, USA. Their critical habitat has been broadly defined, with little empirical ...data on habitat use to direct management actions. This article examines data collected during surveys for a long‐term photo‐ID study to gain insight into the use of critical habitat by CIBW groups and individuals, with a focus on areas where belugas were observed feeding, calving, rearing young, and in transit. It also describes patterns of group distribution, size, and composition, according to sex and age class, in order to better understand how CIBWs are distributed throughout critical habitat during the ice‐free season. The results are presented according to survey month and survey zone, so that patterns of habitat use are accessible in a useful format to aid managers in evaluations of how timing and location of human activities occurring in CIBW critical habitat may overlap with CIBW occurrence and use of these areas.
2.There were 575 beluga groups encountered during 477 photo‐ID surveys conducted in CIBW critical habitat 2005–2017. CIBW locations were mapped, and models were developed to test for temporal and spatial patterns. Approximately 400 individual whales were identified, and their sighting histories were compiled to examine residency and movement patterns.
3.CIBWs were found seasonally in distinct areas, where they aggregate in large groups of both sexes and all age classes while rearing calves and feeding. These areas, and the general corridors connecting them, represent important beluga habitat that warrant focused management attention and protection efforts.
4.Whales travelling among distinct areas of Cook Inlet increase their likelihood of exposure to multiple, localized threats.
5.Habitat protection and the regulation of anthropogenic activities should consider cumulative effects of all activities in the range of CIBWs and their potential to affect the entire population.
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