Biology subjects

Bortolotto, G. A.

Publications and source records attributed to Bortolotto, G. A..

3 recordsLinked to original sources

bioRxiv2022

Weddell seals near the fastest melting glacier in Antarctica prefer shallow, coastal and partially ice-covered waters

Antarctic ice-shelves melting is accelerating, and the highest rates for the continent are observed in the Amundsen Sea, where Weddell seals are understudied. By modelling an unrivalled telemetry tracking dataset, we show that this top predator in the area is more likely found in shallower waters, closer to the coast, half-covered by ice and where the temperature at the ocean bottom is around 0.5{degrees}C or colder. Their distribution during winter is more restricted to coastal areas in the eastern Amundsen Sea and spread out in warmer months. That fluctuation reflects the drastic variation in their habitat illustrating their potential sensitivity to the upcoming impacts of climate changes. We discuss their overlap with Antarctic toothfish fisheries in the area and the potential consequences of global warming to the ecology of the seals.

ecology↗

bioRxiv2022

Critically endangered franciscana dolphins in an estuarine area: fine-scale habitat use and distribution from acoustic monitoring in Babitonga Bay, southern Brazil

Franciscana dolphins in Babitonga Bay represent the only population of that critically endangered species which is confined to an estuary. Surrounded by large cities and harbors, that environment presents intense human activities and potential impacts that may threaten the dolphins. Understanding their habitat use and distribution can inform mitigation of such impacts. Here we used acoustic data from sixty fixed passive acoustic monitoring stations, implemented between June and December 2018. The relationship between the occurrence of franciscanas and environmental variables was investigated with generalized additive mixed models. The selected model presented 51% of explained deviance and included "time of day", "intensity of presence of Guiana dolphins", "maximum slope", and "bottom sediment", among other less statistically significant variables. A daily distribution pattern was identified, with franciscanas remaining in the areas of greatest occurrence especially in the morning and seemed to prefer sandy bottom and flatter areas. Areas intensively used by Guyana dolphins were avoided. Additionally, we mapped their distribution using "Empirical Bayesian Kriging" to identify the main areas of occurrence and for foraging. Franciscanas are consistently predominant in the innermost region of the estuary, without expressive use of the entrance channel, but with a wider range in winter than in the spring. The area around the islands, between the north and south banks, represents an important foraging area, a behavior more frequent during dawn and night. This study provides important insights into critical habitat and behavioral patterns of franciscanas, especially this critically endangered population.

ecology↗

bioRxiv2022

Aerial survey perspectives on humpback whale resiliency in Maui Nui, Hawai'i, in the face of an unprecedented North Pacific marine warming event

After decades of population growth, the central stock of the North Pacific population of humpback whales, known as the Hawaii Distinct Population Segment (HDPS), was delisted from its endangered status in 2016. At that time, however, an unprecedented heating event, the "Pacific Marine Heatwave" (PMH) was already underway. The PMH coincided with reports of major declines of sightings of humpback whales, including calves of the year, on both the Hawaiian wintering grounds and the feeding grounds of Southeast Alaska. To examine the resiliency of the Hawaii Distinct Population Segment, we conducted aerial surveys of the high-density Maui Nui region immediately following the PMH event in 2019 and 2020, using distance sampling methods identical to those used in an earlier series (1993 to 2003). Results showed whale densities at or above those seen earlier, with mean density for 2020 highest overall. Crude birth rates (% groups containing a calf) were similarly comparable to those recorded in the earlier series, with an increase from 2019 to 2020. Overall, results suggest the central North Pacific humpback whale population stock to be resilient in the face of this major climatic event.

ecology↗