Latin American Journal of Aquatic Mammals (LAJAM)
Not a member yet
358 research outputs found
Sort by
Biopsy darting of common bottlenose dolphins (Tursiops truncatus) in southern Brazil: evaluating effectiveness, short-term responses and wound healing
No full textCetacean biopsy sampling is a widely used technique with undisputable scientific value. Although it is generally considered as a harmless technique with no apparent long-lasting effects, studies have recommended examining behavioral responses to evaluate potential impacts on individuals, groups and sampled populations. In this study, we evaluated individual behavioral reactions and wound-healing in common bottlenose dolphins (Tursiops truncatus) during a biopsy sampling program carried out in southern Brazil from 2003 to 2012, and compared sampling effectiveness between dedicated and opportunistic sampling surveys. Two hundred and fiftytwo biopsy attempts were made, resulting in 118 hits (48% of attempts) and 134 samples (52% of attempts) collected successfully. Responses to biopsy sampling were low-level, of short-term duration, and elicited similar reactions on the dolphins, irrespective of shot distance, sex of individuals, dolphins’ group size and pre-behavioral state. Dolphins subjected to multiple biopsy attempts reacted in a similar manner as in previous attempt(s), with no evidence of increasing the intensity of the reaction. Wounds could be monitored in 18 animals and healed over 18 to 35 days. Generally, wounds appeared to be covered by epidermis in about three weeks with no observed signs of skin infection. Our results agree with previous studies suggesting that biopsy sampling does not cause significant disturbance to the behavior of dolphins. At a local level, this study demonstrates that biopsy sampling of bottlenose dolphins in the Patos Lagoon Estuary is more effective, less costly and less intrusive when conducted opportunistically, but that long-term sampling is required to achieve a relatively good sample size from photoidentified individuals in the population
Report of the Working Group on Ethnobiology and Environmental Education related to Tursiops truncatus in the Southwest Atlantic Ocean
No full textEthnobiological studies and educational projects related to bottlenose dolphins (Tursiops truncatus, Montagu, 1821) are still incipient in the Southwest Atlantic Ocean (SWAO). We review studies conducted in the region, especially Brazil, where more information is available. Proposals to implement studies related to ethnobiology and environmental education in relation to the species are also presented
Variations and anomalies in the vertebral column of the bottlenose dolphin (Tursiops truncatus) from southern Brazil
No full textThis paper describes cases of morphological variation and bone anomalies in the axial skeleton of the bottlenose dolphin, with emphasis on the vertebral column and considering the physical maturity of those specimens
Long-term site fidelity and residency patterns of bottlenose dolphins (Tursiops truncatus) in the Tramandaí Estuary, southern Brazil
No full textThe occurrence of common bottlenose dolphins (Tursiops truncatus) in Tramandaí Estuary, southern Brazil, is described based on a photo-identification study conducted between January 2009 and February 2010. A total of 128 survey days were conducted with an average observation effort of 2.6 hours per day (SD = 0.6). Approximately 2050 photographs were taken from a shore land location at the mouth of the estuary. A total of nine dolphins were identified, including three calves. The dolphins were observed during all seasons, with a greater frequency during fall (79.3% of the days) and winter (60.7% of the days). The summer presented the lowest occurrence (2.4% of the days) of dolphins. During the entire study period, the maximum number of individuals sighted in any given day ranged from one to seven (average = 2.8 dolphins; SD = 1.35; n = 51). The residence indices, based on the resighting frequency of dolphins during the study period, ranged from 0.02 to 0.24 (average = 0.13; SD = 0.08; n = 9). However, most of the animals (67%) were resighted in over five months during a year and could be classified as residents. Longterm site fidelity was detected by resightings of four dolphins for over 18 years. These data combined reinforce the importance of the Tramandaí Estuary for the common bottlenose dolphins in the region and highlight the need for local conservation efforts to guarantee the long-term persistence of these coastal populations
Report of the Working Group on the Behavioral Ecology of bottlenose dolphins in the Southwest Atlantic Ocean
No full textIn this report, we present a compilation of the behavioral patterns of bottlenose dolphins and social structure throughout the Southwest Atlantic Ocean. We have compiled and summarized available data concerning: (i) behavioral activities (states and events), (ii) social structures (group size and composition), (iii) acoustic behavior and (iv) intra and interspecific interactions of bottlenose dolphin populations throughout the SWAO, from northern Brazil to southern Argentina. Lack of systematic and standardized methodologies for data collection precludes robust data analyses in respect of bottlenose dolphin behavior. Available information suggests that the studied populations presented weak intra-population associations and that coastal individuals tend to form smaller groups than their oceanic counterparts. Bottlenose dolphins from SWAO produce stylized whistles in which the acoustic parameters are similar to published ranges around the world and some results indicate significant local inter-population variation in the acoustic parameters of the whistles. Data of intra and interspecific interactions of bottlenose dolphins in the SWAO are scarce and therefore do not fully allow a comprehensive analysis of the situational contexts
Report of the Working Group on the Distribution of Tursiops truncatus in the Southwest Atlantic Ocean
No full textThe study reviews the information available on the distribution patterns of bottlenose dolphins within the SWAO (04oN-56oS, 25oW-67oW) including the northern portion of Brazil, covering the period from 1894 to 2011
First estimate of common bottlenose dolphin (Tursiops truncatus) (Cetacea, Delphinidae) abundance off Uruguayan Atlantic coast
No full textThe common bottlenose dolphin Tursiops truncatus is often observed throughout the oceanic coast of Uruguay. Historically, its distribution was wider, including the estuary of the Río de la Plata, but currently its occurrence seems to be restricted mainly to the Uruguayan Atlantic coast (Rocha Department). Conflicting interests and tradeoffs between conservation and development are being generated in Uruguay. On one hand, the establishment of protected areas, responsible tourism and sustainable fisheries are promoted, while on the other hand, foreign exploitation of natural resources and development of mega-infrastructure in coastal zone are facilitated. In this work, we provide the first estimate of bottlenose dolphin’s abundance along the Uruguayan Atlantic coast. These results can be used as baseline information for monitoring population trends and guiding conservation actions for bottlenose dolphins in Uruguay. Mark-recapture models were applied to data of photoidentified animals with long-lasting natural marks. Total population size estimates of 63 individuals (95% CI = 54–74) and 61 (95% CI = 53–73) were obtained from closed and open population models, respectively. Although the estimates are within the range of values obtained for other coastal bottlenose dolphin populations in the Southwest Atlantic Ocean, as well as other regions of the world, it is lower than the values reported for populations inhabiting open habitats. This small population is probably vulnerable to non-natural removals, environmental and demographic stochasticity. Therefore, precautionary actions are recommended given the planned development for this coastal region
Mark-recapture vs. line-transect abundance estimates of a coastal dolphin population: a case study of Tursiops truncatus from Laguna, southern Brazil
No full textCetacean populations in coastal habitats are increasingly threatened by multiple anthropogenic impacts. Monitoring these populations to obtain robust estimates of abundance and detect trends over time is critical to achieve conservation goals. Here, we conducted a pilot study to evaluate the effectiveness of two commonly used abundance estimation methods: mark-recapture and distance sampling line-transect. Surveys were conducted to estimate the abundance of bottlenose dolphins in Laguna, southern Brazil. We implemented power-analysis models and compared both techniques in terms of cost, time and effectiveness to detect trends over a five-year period. Mark-recapture models were analyzed in MARK and resulted in an abundance of 50 individuals (CI = 39-64) with a coefficient of variation (CV) of 0.13. The line-transect models were implemented using the program DISTANCE and resulted in an estimate of 62 individuals (CI = 38-103), with a CV of 0.24. Comparing both approaches, mark-recapture resulted 1.30 time more expensive than line-transect for a single season of effort, but was twice as effective in terms of precision. As a consequence, the probability of detecting a 5% trend during a five-year period is 2.08 times higher with mark recapture. Conversely, the final cost to detect a trend with distance sampling is 1.19 time higher but considering six more years of effort. These results highlight the importance of selecting a-priori sampling design techniques that include developing pilot studies that evaluate the bias, precision and accuracy of estimates while considering costs involved. Considering the small population size estimated herein, the sensitivity of both approaches for detecting trends is not sufficient because the original population would be markedly reduced by the time a declining trend was detected. Thus, a precautionary approach is still imperative, even when robust estimates are obtained
A reliable method for sexing giant otters (Pteronura brasiliensis) in the wild
No full textSexing of giant otters under field conditions is only possible when individuals are entirely out of the water, usually when basking or grooming. Body size is not indicative of gender, and the breeding pair does not necessarily consist of the largest animals in the group. Sexing is facilitated by the presence, in adult, parous females, of four permanently elongated teats (due to repeated and prolonged lactation) and, in mature males, of a visible scrotum. Identification of the breeding male is sometimes assisted his behaviour, specifically that of marking, and by his year-on-year permanence in the group. However, sexing is more difficult in adult females that have not lactated, or in sub-adults, juveniles, and cubs of both sexes. Here, we present a reliable method of sexing wild Giant otters of all ages and sexual status, tested with known sex individuals
Strand-feeding by coastal bottlenose dolphins (Tursiops truncatus) in the Gulf of Guayaquil, Ecuador
No full textStrand-feeding as a predatory strategy was first observed in bottlenose dolphins, Tursiops truncatus, inhabiting waters of Spartina marshes of South Carolina and Georgia, United States. While a substantial body of documented observations exists for many regions of the world, current evidences and photo-documentation of these types of foraging behaviors by bottlenose dolphins in the Pacific coast of South America are scarce. To the best of our knowledge, behaviors resembling strand-feeding by bottlenose dolphins have been described very briefly without supporting photos in the inner estuary of the Gulf of Guayaquil. As a part of a long-term field study (2001-2011) on photo-identification, population ecology and monitoring of the bottlenose dolphin in the El Morro Mangrove and Wildlife Refuge, we provide some insights on its conservation, and photo-documented the occurrence of strand-feeding as a recurrent behavioral foraging tactic in this region of South America