Skull morphological variation in a British stranded population of false killer whale (Pseudorca crassidens): a three-dimensional geometric morphometric approach

The false killer whale (Pseudorca crassidens (Owen, 1846)) is a globally distributed delphinid that shows geographical differentiation in its skull morphology. We explored cranial morphological variation in a sample of 85 skulls belonging to a mixed sex population stranded in the Moray Firth, Scotland, in 1927. A three-dimensional digitizer (Microscribe 2GX) was used to record 37 anatomical landmarks on the cranium and 25 on the mandible to investigate size and shape variation and to explore sexual dimorphism using geometric morphometric. Males showed greater overall skull size than females, whereas no sexual dimorphism could be identified in cranial and mandibular shape. Allometric skull changes occurred in parallel for both males and females, supporting the lack of sexual shape dimorphism for this particular sample. Also, fluctuating asymmetry did not differ between crania of males and females. This study confirms the absence of sexual shape dimorphism and the presence of a sexual size dimorphism in this false killer whale population.

Rare records of the false killer whales (Pseudorca crassidens) in the Adriatic Sea

In spring 2021, four unusual encounters with a group of false killer whales were recorded in Kvarner Bay, Northern Adriatic Sea. A minimum of five individuals, including a calf, were observed and two photos were taken corroborating species identification. These are the first reported sightings of the species in the Adriatic Sea since the mid-twentieth century. In addition, another encounter was revealed that occurred at the end of the 2000s in the same location and should be added to the list of historic observations. These reports were obtained by chance and show the importance of citizen science in obtaining data on rare marine species. The information gathered goes towards a better understanding of the distribution of the species in the Mediterranean Sea.

“Mostri Marini”: Constantine S. Rafinesque's names for three of Antonino Mongitore's Sicilian whales

In 1815, the naturalist Constantine Samuel Rafinesque (1783–1840) previewed three new species of cetaceans – Delphinus dalippus, Physeter urganantus and Oxypterus mongitori – that he intended to describe from Sicily based on illustrations in Antonino Mongitore's published work Della Sicilia ricercata nelle cose più memorabili (1742–1743). Although formal descriptions of the three species were never published, Rafinesque's reference to Mongitore's illustrations made the names available by “indication”. The names, nonetheless, fell into obscurity, most likely a result of contemporary taxonomists' lack of access to Mongitore's work. Rafinesque's names remain relevant to the history of cetacean taxonomy, although they are no longer applicable. Moreover, the animals associated with these names add to the historical record of whale strandings in the Mediterranean. For these reasons, we studied the illustrations Rafinesque indicated for his cetaceans and reviewed Mongitore's accompanying text, which together provide sufficient distinctive characters that two of the three animals can be confidently identified with modern species, namely the sperm whale, Physeter catodon Linnaeus, 1758 , and the false killer whale, Pseudorca crassidens (Owen, 1846). Had Rafinesque's name D. dalippus been recognized for what it was, it would have had priority over P. crassidens as the earliest scientific name for the false killer whale.

The abundance of false killer whale, Pseudorca crassidens (Artiodactyla: Delphinidae) in coastal waters of Golfo Dulce and Osa Peninsula, Costa Rica

Introduction: False killer whale (Pseudorca crassidens) is a tropical and subtropical social species that live in groups with individuals of mixed ages and sex classes. False killer whales have been documented since the late 1990s in Southwestern Costa Rica. Objective: To estimate the abundance of false killer whales in Osa Peninsula waters. Methods: Cetacean surveys off the Osa Peninsula Waters (OPW), Costa Rica, yielded opportunistic encounters with false killer whales in Drake Bay and Caño Island (2001-2015) and observations during formal surveys in Golfo Dulce (2005-2015). Photo-identification data was analyzed using capture-mark-recapture models in the study area, through an open population (POPAN) framework, considering the effect of time on the parameters apparent survival and capture probability, producing an abundance estimate for a superpopulation in the entire study area. Results: False killer whale abundance in OPW is characterized by a small population size of no more than 100 individuals, complemented by a very low probability of encounter and a contrasting high apparent survival. Conclusions: This population estimate should be taken as conservative, however, the small population size of less than 100 individuals should be considered vulnerable, in contrast to the increasing anthropogenic impacts in the coastal seascape. We argue the potential occurrence of population units along the coastal seascape of the Pacific littoral and oceanic island-associated units at Isla del Coco.