Latin American Journal of Aquatic Mammals (LAJAM)
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Killer whales (Orcinus orca) predation on mysticetes in the Gulf of California, Mexico
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Killer whales (Orcinus orca) prey on various whale species in the world’s oceans. Here, we present seven cases of mysticetes preyed upon by killer whales on the continental coast of the Gulf of California. Five fin whales (Balaenoptera physalus), one Bryde’s whale (B. brydei), and one gray whale (Eschrichtius robustus) were preyed upon and partly consumed in the same way over 17 years in different areas of the coast of Sonora, Mexico. The methodology included direct inspection of stranded or floating whale carcasses, analysis of predation marks, and review of videos provided by local fishermen. The notorious way in which whales were preyed upon by cutting and ripping large portions of blubber and skin layers is similar to how the whalers used to flense whale carcasses. No internal organs were consumed, although the tongue was consumed in each event. Most attacks occurred in shallow waters, coinciding with high productivity/upwelling areas. These events provide evidence on killer whales’ hunting behavior and consumption patterns, highlighting the importance of shallow waters and selectivity of the skin/blubber and tongue as preferential food, which contributes to understanding the trophic interactions of cetaceans in the Gulf of California
Extant emergence of Greater Caribbean manatees (Trichechus manatus manatus) in the Virgin Islands: Hopes for the beginning of a natural recolonization process
No full textThe potential of passive acoustic monitoring for the study of ecological interactions among freshwater Amazonian dolphins and fishes
No full textThe acoustic behavior of Amazonian aquatic fauna and the importance of its soundscape are poorly understood. Sounds produced by wild river dolphins (Amazon River dolphin, Inia geoffrensis, and tucuxi, Sotalia fluviatilis) and those of unidentified fishes were recorded from a drifting boat on six different days (8.5 h duration) in July 2012, in the Pacaya-Samiria National Reserve of Peru. Unidentified sounds of fishes were dominated by four broad types: pulsed stridulation, long stridulation, long pulse, and short pulse. Dominant sounds produced by dolphins included echolocation click trains, burst-pulses, whistles, and bubble bursts. Soniferous activity was quantified as total sound duration per 10 s of recording and compared between dolphins and fishes for each sound type and all types combined. Soniferous activity was highly variable among days, with echolocation click trains (7.7 s min-1) and pulsed stridulation (0.33 s min-1) being the dominant components. Soniferous activity of the dolphins and fishes was correlated (Spearman r = 0.49, P < 0.001). However, whether the correlation resulted from predator-prey interactions or other spatial factors could not be determined. Although preliminary in nature, this study is the first examination of the soniferous activity of both river dolphins and fishes in the Amazon and suggests passive acoustic monitoring has the potential to provide unique insight into ecological interactions in the system
A preliminary study on mercury levels in the soft tissues of the Guiana dolphin (Sotalia guianensis) and edible fish from southern Lake Maracaibo, Venezuela
No full textCoastal ecosystems around the world are facing increasing mercury pollution from various anthropogenic activities, which are affecting many aquatic mammals such as dolphins. Lake Maracaibo receives discharges of industrial water, wastewater, pesticides and herbicides from runoff, and constant oil spills; these discharges include several contaminants. In this paper, we highlight the extent of mercury accumulation in the soft tissues of Guiana dolphins and some fish species from southern Lake Maracaibo. A total of 17 fish species were analyzed. All but one of the species had traces of mercury, but only the mercury level in Gobioides broussonnetii (mean ± standard deviation = 0.9209 ± 0.0134 mg kg-1 wet weight (ww)) exceeded the limit established as safe for human consumption. In Guiana dolphins, mercury levels in four of six individuals exceeded the maximum limit considered safe for human consumption (0.5 mg kg-1 ww), with the highest level of 2.9611 ± 0.1637 mg kg-1 ww in the liver of one individual, suggesting biomagnification through diet and possible adverse effects in this species. It is important to note that the dolphins from which samples were collected were juveniles. There is evidence of a correlation between mercury accumulation and the size and age of dolphins, emphasising the ecological risks posed by anthropogenic pollutants. The wider ecological impacts, including threats to endangered fish species and public health risks associated with mercury-contaminated marine resources are also discussed. This study emphasises the urgent need for comprehensive management strategies to reduce mercury pollution and to protect coastal ecosystems and public health
The return of the giant otter (Pteronura brasiliensis) to Tauramena (Casanare, Colombia): relative abundance, distribution, and conservation considerations
No full textThe giant otter (Pteronura brasiliensis) is endemic to South America, and in Colombia it is distributed in the Amazon and Orinoquia regions. It inhabits rivers, streams, and lagoons, but prefers the latter two in response to resource availability depending on the season. Giant otters are endangered in Colombia, and aspects of their natural history are still unknown in much of their geographic range. Our research aim is to generate information focused on relative abundance, habitat use, and distribution of the giant otter in an area of Colombia where it was thought to be extirpated. The distribution was evaluated with spatial distribution modeling (SDM) and habitat use using the Wallace 2.0.4 package for the department of Casanare in northeastern Colombia. To assess the population status and abundance in the municipality of Tauramena, 30 transects were surveyed in the Tua River and the Piñalito and El Huesero streams in 2021 and 2022. In general, the distribution models highlighted the importance of precipitation, temperature, and forests for the occurrence of this species. In Tauramena, five family groups were detected, which were composed of an average of 4.83 ± SD 3.16 individuals per group and a relative abundance of 1.03 ind./km. These are positive results for giant otters, as they indicate signs of population recovery of a species previously thought to have been extirpated from this region because of hunting and illegal pelt trade. Even though Tauramena is an area with high levels of anthropic disturbances, giant otters are showing signs of adaptability and plasticity, which provide important conservation opportunities. It is expected that this work will become the first step for the generation of additional information on diet, behavior, and population structure that can inform management plans for the giant otter in Colombia
Status of the offshore California sea lion (Zalophus californianus) rookery within the Guadalupe Island Biosphere Reserve, Mexico
No full textHelminth parasites and epizoites in common dolphins (genus Delphinus) from coastal Peru and Ecuador
No full textA twenty-five year old dataset of parasites in long-beaked and short-beaked common dolphins (Delphinus spp.), using fisheries as an opportunistic platform of access, registered seven species of helminths and one epizoite, being a unique dataset for the Southeast Pacific. Sampling was conducted in 1985-2000 at six fishing ports in Peru and Ecuador where cetaceans were landed from interactions with small-scale fisheries. From a total of 473 common dolphins examined, we identified helminths including three species of Trematoda: Nasitrema globicephalae, Pholeter gastrophilus, and Braunina cordiformis; three species of Nematoda, including Anisakis spp., Crassicauda spp., and Halocercus sp.; and two cestodes, Tetrabothrius forsteri and Clistobothrium delphini. No acanthocephalans were observed. No statistically significant sexual and ontogenetic variation in helminth prevalence was detected, after which samples were pooled. The highest prevalences in the long-beaked common dolphin (n = 440) were observed for N. globicephalae (87.9%, 29 infested/33 sampled) in cranial sinuses, Crassicauda sp1. (80%, 4/5) in mammary glands, followed by Cl. delphini (28.6%, 2/7) in the blubber, and P. gastrophilus (23%, 26/113) in the pyloric stomach. Although comparative testing was unfeasible due to minimal samples of short-beaked common dolphin (n = 33), several of the same helminth species were found; but not N. globicephalae nor B. cordiformis. No cyamids were encountered while pseudo-stalked barnacles Xenobalanus globicipitis were common. Although no new (global) helminth host records were revealed for common dolphins, this study presents a first checklist of parasites separately for the Southeast Pacific long-beaked and short-beaked common dolphins. Future work should include exhaustive laboratory-based necropsies, enhanced sampling of the short-beaked form, review data from recent parasite collections, focus on intermediate hosts and parasitic pathology, including potential human health impact from consumption of small cetaceans
Identifying spatial conservation priorities for the giant otter (Pteronura brasiliensis)
No full textThe giant otter (Pteronura brasiliensis) is a charismatic, South American, social carnivore, and the largest otter species in the world. Historically, giant otters were almost extirpated due to the wildlife skin trade and are currently considered as Endangered. Using the Range Wide Priority Setting methodology, we (a group of 33 giant otter experts) updated the species’ historical range (9,021,590 km2), modelled an adjusted and more conservative aquatic historical range of 2,813,539 km2, systematized 5,593 giant otter distribution points across the range, and identified geographic areas for which there was expert knowledge (63%), including areas where giant otters no longer occur (19%), and geographic areas where giant otter presence is uncertain due to a lack of expert knowledge (37%). To prioritize conservation actions into the future and identify existing giant otter population strongholds, we used expert knowledge to identify 22 of the most important areas for the conservation of the species (i.e., Giant Otter Priority Conservation Units [GOPCUs]) that cover 29% of the historical range, and range in size from 1,367 km2 to 829,152 km2. In general, GOPCUs were relatively large and approximately 35% of the total GOPCU area is already designated as protected areas. Using the Range Wide Priority Setting results, we make a series of recommendations towards the long-term conservation of this iconic aquatic species