Marine Mammal Science最新文献

Deraniyagala's beaked whale (Mesoplodon hotaula) is one of the least-known beaked whale species, with only a few of possible live sightings being documented to date. Here, vocalizations of Deraniyagala's beaked whales were recorded using drifting recording systems in the confirmed presence of this whale in the northern South China Sea (SCS) in 2021. A total of 699 qualified frequency-modulated (FM) pulses were used to calculate frequency and duration measurements. FM pulses had a median peak frequency of 43.3 kHz and median interpulse interval (IPI) of 244.6 ms. Both the spectra measurements and clustering analysis showed the recorded clicks closely resemble the clicks of beaked whales at Palmyra Atoll (presumed to belong to Deraniyagala's beaked whale). Compared with other Ziphiidae species, interspecific differences were also observed. Distinguishing between Deraniyagala's and ginkgo-toothed (M. ginkgodens) beaked whales with acoustic data sets seems to prove feasible. Our results also suggested that Deraniyagala's beaked whales may produce more than one subtype of FM pulses. This study presents the first description of echolocation clicks produced by this species based on the confirmed visual sightings. It is beneficial to identify the species in passive acoustic monitoring records and gain further insight into this species' vocalizations.

Acoustic communication is an important aspect of life for marine mammals, as their environment often limits the reliability of visual cues. However, there is little information regarding the acoustic communication and behavior of Australian snubfin dolphins (Orcaella heinsohni). This study was designed to determine if call rate and type were significantly affected by the behavioral state, group size, and cohesion of snubfin dolphins in the Fitzroy River in Queensland, Australia. We found that dolphins significantly modified both call rate (calls/hour/individual) and call type among behavioral states. For example, call rates were higher when dolphins were foraging versus resting or traveling. We also found that group size and cohesion had minimal effects on call rate, but significantly affected the predicted probabilities of call type production. For example, the probability ratio of burst pulse to whistle production is estimated to be highest when groups are widespread (>10 m), indicating the potential importance of burst pulses in maintaining contact between dispersed individuals. This study presents the first comprehensive analysis of snubfin dolphin communication under natural noise conditions in relation to behavioral context, which provides a foundation to explore how anthropogenic acoustic masking and behavioral disturbances may affect these dolphins in the future.

Stranded marine mammals provide valuable insight into population health of free-ranging conspecifics; however, the likelihood of carcass detection by the public or trained observers is not well known. To better understand carcass detection rates (CDR), we placed twelve decoy dolphin carcasses around Dauphin Island, Alabama, for 2 weeks, one during peak tourist season and one during the off season. Decoys were placed in regions representing different habitat types (marsh or beach) and levels of human use (low or high). Calls from the public were recorded, and trained observers actively searched for decoys via drone and visual observation either by vessel or UTV and walking. There were 2.5 times more public reports during the peak (n = 38) compared to off season (n = 15), with most reports being from the high-traffic beach site during peak season (n = 27). Trained observers found more decoys (CDR = 0.88) than the public (CDR = 0.58), however, the public found two decoys that observers did not. Drone searches were slightly more successful (CDR = 0.83) than other methods (CDR = 0.79). Our results indicate that a combination of surveillance methods will enhance carcass detection, and our novel methods can be used across habitat types to improve stranding surveillance, better estimate stranding rates, and inform mortality estimates of many species.

Vocalizations are potential indicators of pain in animals. We recorded and analyzed spectrographically the vocalizations of harbor seal pups (Phoca vitulina) before, during, and after the routine procedures of flipper tagging and microchipping prior to release from a rehabilitation facility in British Columbia, Canada. It is standard practice for these procedures to be done without analgesia. In Experiment 1, we compared vocalizations before and after the procedures (n = 21); in Experiment 2, we compared vocalizations in response to real and sham procedures (n = 10). In Experiment 1, seals produced more vocalizations, and peak frequency was higher, after tagging and after microchipping. In Experiment 2, seals also produced more vocalizations after real but not after sham tagging and microchipping. The average peak frequency was higher after each procedure, but not after each sham procedure. These results suggest that an increase in the number and peak frequency of vocalizations are indicators of pain in seal pups. The results also suggest that analgesia, when feasible, should be considered for harbor seal pups undergoing routine flipper tagging and microchipping.