The notion that ‘Stock-G’ humpback whales off western South America are primarily deep oceanic migrators is poorly supported. We documented 66 land-based sightings from Pucusana, Lima Sur: 18 incidental (2002–2023) and 48 dedicated sightings during the northbound winter migration (June-July 2023), covering respectively 38 and 105 individual whales, despite a mean daily observer effort of only 58.7 min. Estimated distances from shore ranged 20–7,000 m (mean= 2,729 m) at depths 25–99 m, while 50% migrated at < 2,500 m (median) from shore. Several groups skirted the coastline from headland to headland. Of five southbound migrating groups, four included an adult with neonate; no northbound groups enclosed a neonate. Two cases of single juvenile/subadult whales moving multidirectionally and closely associated with large seabird feeding frenzies, were considered foraging also. In 2023, 94% of all northbound nearshore sightings occurred from 14 June-11 July, signalling the maximum threat period for interactions with coastal fisheries off metropolitan Lima. If migration is temporally and spatially predictable, effective mitigating measures should be feasible.

Small-boat and shore-based surveys in 2017 confirm that Atlantic humpback (Sousa teuszii) and common bottlenose dolphins (Tursiops truncatus) are resident in shallow neritic waters surrounding the protected MPA Tristao Islands in northern Guinea. Inshore-type T. truncatus were encountered also between Conakry and Kayar. First documented in 2012, dolphin bycatches in local fisheries continue to occur. The frequency of beach-cast remains suggests a significant conservation issue. Both multi- and monofilament gillnets are widely deployed, but it remains unclear which gear is the main cause of mortality. Forensic evidence shows that captured dolphins are often utilized for local consumption. Marine bushmeat of cetaceans is documented in many coastal nations in West and Central Africa. In Tristao Islands their use is synchronous with and thought related to declining fish stocks. Significant anthropogenic mortality relative to their low abundance, besides suspected pressures such as prey competition with fisheries and habitat deterioration from coastal development, raise concern for the future of coastal dolphins, in particular endangered S. teuszii, even in this formally protected MPA. Conservation measures need to be re-evaluated for improved efficiency while surveys to monitor trends should be annual.

We present the first evidence of lethal interspecific aggressive behavior against Burmeister’s porpoise Phocoena spinipinnis, in a non-predatory context, and the first indications of such behavior in a cetacean from Chilean waters. Two cases, both adult males, are described. Analysis of the fresh tooth rakes, specifically the inter-rake distance, points to common bottlenose dolphin Tursiops truncatus as aggressor. Interdental distances measured on skulls allowed us to exclude Orcinus orca, Globicephala melas, Lagenorhynchus obscurus and Pseudorca crassidens. Evidence of severe blunt trauma, including extensive subdermal hematomas, rupture of pleura and extrusion of lung parenchyma, underscores the level of violent aggression. The reason is unknown but Tursiops truncatus is well-documented to occasionally harass and kill harbour porpoises Phocoena phocoena in the Northern Hemisphere. Considering the scarce information available on the biology and behavioral ecology of Burmeister’s porpoises in Chile and elsewhere, we recommend more systematic field research. Also, as to help formulate effective management measures that can mitigate the main threat for this species in Chile (as in Peru), i.e. fisheries interactions. In Chile, P. spinipinnis is classified as Data Deficient (D.S. N°06-2017), so its real conservation status is unknown.

Few reports exist on the pathologies of the northern bottlenose whale (Hyperoodon ampullatus) and other Ziphiidae. We here describe a large exostosis in the right pterygoid bone of adult female H. ampullatus ANSP-3004 that stranded on the US Atlantic coast in 1867. Images of the skull and 14 cranial measurements were examined and compared with two ‘normal’ adult female H. ampullatus specimens. Surface scans of ANSP-3004 were made with a Faro Design Arm 1.0 scanner at 75µm resolution. The form, structure and width (15.9 cm) of the right pterygoid were found to be abnormal. Its distal extremity was curved in labial direction while its proximal extremity was deformed by a large, bulbous exostosis of 14.3 x 12.5 cm that partially obstructed the right nasal passage. Lytic lesions in the posterior end of the exostosis exposed deep resorption lacunae. The left pterygoid was thin (3.4 cm) and laterally displaced. No diagnosis was possible for lack of histological examination but the osteopathy was consistent with osteoma, a benign bone tumor commonly seen on the jaws and nasal sinuses of bovines, phylogenetical relatives of Cetacea. The partial nasal passage obstruction may have affected respiration to some degree, but since the female was lactating, general fitness appeared stable.

The Chile-Peru subpopulation (CPe) of the southern right whale (Eubalaena australis) is classified as critically endangered following intense whaling in past centuries. Due to their very low abundance, information on breeding and feeding grounds is also scarce. Unmanned aerial vehicles (UAVs) are increasingly applied in marine mammal research thanks to their low cost and relative ease of use. This case study documents a southern right whale nursing in Bahía Moreno (23ºS), Antofagasta, northern Chile, through high-resolution images taken by UAV of a lone adult in July 2019 and the same (photo-identified) whale with a neonate in August, confirming local parturition. Combined with earlier data we hypothesize that the Antofagasta Region may be a calving and nursing ground for the CPe subpopulation. Given the intense shipping traffic and fishing activities around the Mejillones Peninsula and Antofagasta port, priorly recommended marine spatial planning to help avoid net entanglements and vessel collisions of fin and humpback whales would also contribute to the conservation of the CPe stock of southern right whale.

Humpback whales perform long migrations from their breeding and nursing areas at low latitudes to feeding grounds at high latitudes. Nonetheless this strictly dichotomous paradigm of migration is challenged by accumulating examples of occasional or regular feeding in tropical or subtropical areas for several stocks worldwide. Here we report multiple lines of evidence of IWC ‘Stock G’ humpback whales feeding in coastal waters at low latitudes of the Southeast Pacific Ocean. Lunge-feeding behavior was observed in Ecuador, while both lunge- and trap-feeding in pursuit of Peruvian anchovy was documented in northern Chile. Five records of substantial defecation in a key breeding ground in Ecuador also demonstrates local foraging. In addition mark-recapture analysis of one individual feeding at high and mid latitudes of Chile suggested potential site fidelity to two foraging areas. Whether these behaviors are novel due to changes in prey distribution, intensifying competition for food from a growing humpback whale population, or rather reflect vastly increased research effort in a poorly studied region, remains unknown. Further research into the feeding ecology of 'Stock G' should help reveal historic and potentially novel feeding grounds, prey composition and precise migration paths.

Beaked whales (Ziphiidae) are rarely reported in the Arabian Sea. Four new cases (five individuals) were documented in deep waters offshore Pakistan through a pilot programme in 2015-2018 where trained fishers video-recorded net entanglements in the pelagic tuna drift gillnet fishery. Videos were analysed frame-by-frame. The large body size (est. 5-6m) of one specimen, its moderately bulbous melon, long tubular rostrum and a large falcate dolphin-like dorsal fin, indicated Longman’s beaked whale Indopacetus pacificus. It represents the first record for Pakistan (EEZ), and with a stranding at Gujarat, India, a second for the northern Arabian Sea. The other 4 ziphiids were significantly smaller (est. 3– 4.5m), with a decidedly non-bulbous melon, variable short to moderately short rostra, falcate to subtriangular dorsal fin and a nondescript greyish colouration, identified as Mesoplodon spp. Video quality was poor but none of the specimens showed tusks, arched mandible lines or noticeable linear tooth rakes, practically excluding adult males. The successful release of all net-entangled beaked whales is unprecedented. The simultaneous bycatch of two mesoplodonts in the same net set is equally exceptional. This citizen science strategy adds to our understanding of the distribution of I. pacificus and mesoplodonts, which may be more common in the Arabian Sea than the scarce literature suggests. If significant bycatch of beaked whales is confirmed, the massive tuna gillnet fishing effort in the Arabian Sea could have negative implications for their conservation status.

The morphology and maturation process of gonads of 70 Burmeister´s porpoises, with body lengths ranging 135–183 cm (n= 34 females) and 64.5-182 cm (n= 36 males) were described. Samples were collected in six ports of central and northern Peru in 1987-1999. In the field, females were classified as immature, mature (resting, lactating, pregnant) and males as immature, pubescent and mature based on, respectively, the presence of ovarian corpora and the relative quantity of semen in cut epididymides. The ovaries of P. spinipinnis are ovoid or bean-shaped and flattened, with corpora modifying surface appearance. In the laboratory, ovaries were examined macro- and microscopically, measured, weighed and sliced in 1-3 mm sections. The number of corpora ovarica (lutea, albicantia, atretica) found in each ovary as well as their macroscopic and microscopic characteristics were documented in some detail. The follicles, their oocytes and nucleus were measured. Follicular development in P. spinipinnis is predominantly left-sided, but occurs in both ovaries in 16.3% of females, mainly in those with numerous corpora. Macroscopically, several corpora atretica with luteinization had characteristics similar to those of corpora albicantia, making microscopic determination essential. Inconclusive evidence of recent ovulation was found in January. Two of three immature females showed good follicular development in March and April. The body length at 50% sexual maturity in females was estimated at 152.7 cm. There was no evidence of reproductive senescence. The testes of P. spinipinnis are elongated and cylindrical. Of the 36 males examined macroscopically, 7 were immature, 5 pubescent and 24 mature. The histological analysis determining the presence and abundance of Sertoli cells, spermatogonia, spermatocytes, spermatids and spermatozoa, the relative amount of interstitial tissue, the elongation and mean diameter of the seminiferous tubules and the relative size of the lumen allowed to confidently determine sexual maturity status. The field evaluation of maturity based on the presence of sperm in the epididymides is a useful but, in 8.3% of cases, not exact method. For males the body length at 50% sexual maturity was estimated at 157 cm. No histological evidence of male reproductive seasonality was found. Spermatogenesis was perceptible year-round and tubule diameters had non-specific variations for each month.

Data on helminth parasites and epizoites is presented for the long-beaked and short-beaked common dolphins from the Southeast Pacific. Sampling in 1985-2000 was conducted mainly at six fishing ports in Peru and Ecuador where cetaceans were landed. From a total of 473 common dolphins sampled, we identified helminths including three species of Trematoda: Nasitrema globicephalae, Pholeter gastrophilus and Braunina cordiformis; three species of Nematoda, which includes Anisakis spp., Crassicauda sp. and Halocercus sp.; and two cestodes Tetrabothrius forsteri and Clistobothrium delphini (formerly Phyllobothrium delphini). No acanthocephalans were observed. No statistically significant sexual and ontogenetic variation in helminth prevalence was detected after which samples were pooled. The highest prevalence in the long-beaked common dolphin (n=440) was observed for N. globicephalae (96.3%) in cranial sinuses, Crassicauda sp. (83.3%) in mammary glands, Crassicauda sp. (78.8%) infesting the cranial sinuses, followed by Cl. delphini (28.6%) in the blubber and P. gastrophilus and B. cordiformis (20.4%) in the digestive tract. 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. No new (global) helminth host records are revealed for common dolphins, but 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, focus on intermediate hosts and parasitic pathology, including potential human health impact from consumption of small cetaceans.