Marine Mammal Science最新文献

Large “super-groups” of feeding humpback whales (Megaptera novaeangliae) have occurred regularly off the West Coast of South Africa since ca. 2011, but little is known about their feeding behavior. We used opportunistic underwater video footage to investigate near-surface lunge feeding behavior, group coordination, and the use of pectoral fins in feeding. We analyzed 113 min of underwater video footage collected over 6 days. Whales passed through the frame on 623 occasions and were seen actively lunging on 182 occasions. No lateralization or coordinated foraging was observed. Gape cycles were short (mean mouth opening phase: 2.38 s and mouth closing: 1.69 s) with buccal pouch draining lasting the longest (15.61 s) and being a mostly passive action. The whales often surfaced while the pouch still contained water. Lunges and draining took place in all directions but mostly at ascending and even near vertical angles. Active flipper movements were observed during 81% of feeding lunges, providing further evidence that these uniquely large appendages are used hydrodynamically when feeding and may also play a role in prey herding. Disruption of feeding by diver presence was low. This study provides novel insight into the feeding behavior of Southern Hemisphere humpback whale super-groups, and potential human-whale interactions.

Deaths of wild cetaceans are rarely observed, particularly when not associated with acute anthropogenic interactions, stranding, or entrapment. Even for closely monitored populations, such as the exclusively fish-eating “Northern Resident” killer whales (NRKW; Orcinus orca ater) of the eastern North Pacific, mortality can typically only be assumed when well-documented individuals go missing from otherwise consistent social groupings (Towers et al. 2020). Consequently, the social behavior and ecological context surrounding the majority of deaths remain unknown, though killer whales from multiple discrete populations have been documented exhibiting epimeletic behavior toward deceased conspecifics (Bisther and Vongraven 2022; Shedd et al. 2020). We present the following observations on the death of an adult male NRKW, I76, in Johnstone Strait, BC, Canada.

I76 was a regularly seen individual in the region during summer and had been documented every year since his birth in 1997; he traveled with his mother I4 (born in 1980), his younger sister I102 (born in 2003), and I102's son, I172 (born in 2022). This group, collectively known as the I4s, is considered part of the I11 pod in G clan (Towers et al. 2020). Along with the rest of the I4s, I76 was documented in robust condition and actively foraging on July 27, 2024, at Goose Bank, B.C. The family was next documented on August 28, 2024, in Blackfish Sound, BC, where I76 presented with a minor depression behind the blowhole indicative of reduced body condition. He and his kin were not documented again until August 16, 2025, when community members observed Pacific white-sided dolphins (PWSD; Aethalodelphis obliquidens) and two humpback whales (Megaptera novaeangeliae) interacting with I76 in Blackfish Sound (Figure 1A). Photographs taken at that time indicated that he was in visibly poor body condition.

On August 17, 2025, both authors set out from Alert Bay, BC, with the intention of documenting I76 and his kin. Working from a 7 m rigid-hulled inflatable boat (RHIB), we encountered I76 at 1054 at 50°32.52′N, 126°42.48′W in Johnstone Strait, where he was conducting short, shallow dives (30–60 s) within 2–3 m of the water's surface. Boat-based photographs taken from a distance of ≥ 30 m at that time indicated a pronounced loss of adipose tissue at I76's nuchal crest, consistent with severe emaciation in killer whales and other cetaceans (Figure 1B; Fearnbach et al. 2018; Joblon et al. 2014). No other vessels were within 500 m of I76, though several private and commercial boats were in Johnstone Strait that morning. At 1112, we launched a DJI Mini Pro 4 drone and conducted a short (< 20 min) photogrammetry flight, not lower than 20 m, to collect still images and videos of I76 (Figure 1C). I102 and I172 were concurrently observed traveling along the southern shoreline of Hanson Island, approx

Acoustic studies for any cetacean species in tropical Atlantic Ocean waters are scarce, especially for oceanic dolphins, such as the melon-headed whale, Peponocephala electra. Here we describe a unique visual and acoustic record for this species, filling an information gap about the acoustic patterns of these delphinids in this part of the globe. Recordings were made using a towed array with four hydrophones along with sightings and photographs validating the species identification. We describe 10 acoustic parameters of the melon-headed whale whistles and compare the results with four other studies published for the species in the Pacific and Indian Ocean. Our results show that for most parameters related to whistle frequency, values were higher than those reported in comparable studies for the same species. The whistles are short in duration, and most have a downsweep contour type, followed by an upsweep. The description of acoustic parameters for odontocetes is useful for the development of automatic species-specific whistle detectors. Furthermore, the record of the species in this previously unsampled area sheds light on the patterns of occurrence and distribution of melon-headed whales on a global scale.

The Iberian killer whale subpopulation was assessed as critically endangered (CR) by the IUCN red list of threatened species based on the available information until 2011 on its low abundance, high newborn mortality, and dependency on the endangered Atlantic bluefin tuna. The present study focuses on updating the subpopulation demographic parameters between 2011 and 2023. Data were based on photo-identification and stranding records. Abundance, survival, reproductive rates, and population growth were estimated through mark-recapture models. Stranding records were used to estimate body size and calving seasonality. Sightings of newborn calves were also used for assessing seasonality. From 2011 through 2023, 26 stranding records were obtained, and 18,554 ID-images were examined. This subpopulation showed a stable abundance, with 37 individuals in 2023, still qualifying for the IUCN CR category under criteria D. Calf survival rate has increased compared to pre-2011, while adult survival has decreased, particularly for females. Reproductive rates were low, with an estimated interbirth interval of 8.3 years. The overall population growth rate was apparently stable at 0.46%. Most births occurred in the summer and fall. Iberian killer whales are generally smaller than the average body length of other killer whale populations throughout the world. The study emphasizes the need for long-term monitoring and highlights new potential threats from fishing activities and recent disruptive interactions with recreational boats. The future of the subpopulation depends on recruitment and survival of juveniles and effective female reproduction.