Movement patterns of humpback whales (Megaptera novaeangliae) reoccupying a Brazilian breeding ground

Abstract

The population of humpback whales from breeding stock A is increasing, and little is known about the routes used by humpbacks that move north of the main calving area of Brazil, the Abrolhos Bank. The aim of this study was to describe the movements of humpback whales in a reoccupation wintering area (Serra Grande, Bahia state, Brazil) based on land-based surveys to test if movement patterns change during the season and between years, due to group composition, behavioral state, and distance to the coast. The mean leg speed of the groups sighted was 6.88 (±2.92) km/h, and leg speed was positively correlated with distance to the coast. There was an increase in leg speed and distance to the coast with increasing number of escorts in the groups with calves. The mean linearity value for group trajectory was 0.81 (±0.19) and the mean reorientation rate was 25.72 (±19.09) º/min. We observed a predominance of trajectories heading south throughout the study. Groups exhibiting more erratic movements early in the season, and groups moving south showed more linear trajectories than groups moving north, indicating the beginning of their migration back to the feeding grounds. Energy conserving strategies and social context affect the movements of humpback whales in Serra Grande, resulting in the observed patterns of the reoccupation of available and suitable habitat north of Abrolhos. Thereby, special attention should be given managing activities with the potential to disturb or displace whales using the region to calve and breed.

Energetic Effects of Whale-Watching Boats on Humpback Whales on a Breeding Ground

“…groups with calves (Carvalho-Gonçalves et al, 2018;Bejder et al, 2019). Mother and calf groups face physical and physiological challenges, because calves are learning social skills, have less muscle strength, and lung size compared to adults.…”

Abrupt change in humpback whale song from Brazil suggests cultural revolutions may occur in the South Atlantic

“…However, with this population recovering from commercial whaling, we observed the expansion of the species distribution. There has been a reoccupation of areas that were used by whales before whaling, such as off Serra Grande to the north of the Abrolhos Bank (Andriolo et al, 2010; Gonçalves et al, 2018a,b). Data were collected in these two areas, approximately 400 km apart, both in Bahia state, northeastern Brazil (Figure 1).…”

“…LSI calculation showed that only one 2018 recording has an index value >0, when T A B L E 1 Samples analyzed with respective dates, locations, names of the WAV files, sampling rate (Hz), bit depth, recording duration in minutes, number of full song cycles present, whale group number based on sightings, and the minimum number of singers recorded. As the recordings used from Serra Grande are from different days, we considered that they are from different singers because the probability of recording the same singer on different days is small due to the great mobility of humpback whales in that area (Gonçalves et al, 2018a). compared to 2017 recordings, and the average LSI value comparing all 2017 to 2018 recordings is 0.01 (Figure 3).…”

Surface activity of Humpback whales Megaptera novaeangliae (Cetacea, Mysticeti) on the northern coast of Bahia, Brazil

“…Along the Antarctic coast, humpback whales form different populations during the foraging season in the summer (Baker et al, 1995;Rizzo & Schulte, 2009;Andrews-Goff et al, 2018), but they migrate to the tropical areas during the winter to breed in shallow and warm waters near the coast of the continents (Lunardi et al, 2008(Lunardi et al, , 2010Zerbini et al, 2011;Gonçalves et al, 2018). One of these populations migrates to the Brazilian coast, concentrating in the Abrolhos Bank (southern Bahia State), which is considered the principal breeding area of the species (Rossi-Santos et al, 2008;Wedekin et al, 2010;Ristau et al, 2020).…”