| Azorean Species | Atlantic Spotted dolphin – Stenella frontalis – Golfinho-pintado-do-Atlântico
Scientific Name: Stenella frontalis (G. Cuvier, 1829)
Common Name (UK, FR, PT, ES, DE): Atlantic spotted dolphin, Dauphin tacheté de l`Atlantique, Golfinho-pintado-do-Atlântico, Delfín pintado, Zügeldelfin. (Jefferson et al. 2015).
Short Species description: These animals are toothed cetaceans (suborder Odontoceti) with a wide variation in color pattern as they develop. They are born without spots and as they get older the spots develop on the ventral and dorsal surfaces. In body shape they are neither too robust nor too thin. Newborn dolphins are between 0.8-1.2 m long and the adults are up to 2.3 m long with a maximum weight of 143 kg (Jefferson et al. 2015).
The diet of these species consists of epi- and meso-pelagic fishes, squid and benthic invertebrates. Longevity is not well known (Jefferson et al. 2015).
Population status: Least Concern (overall species) by IUCN status.
Occurrence in the Azores (including season): Seasonal in the Azores and occur during late spring to late summer (June-October) arriving with the warm waters of the Gulf of Mexico. This species is one of the most sighted during the summer months in the Azores. They approach and interact with the boats and are avid bowriders. These dolphins can be observed in mixed pods with common bottlenose dolphins (Tursiops truncatus), common dolphins (Delphinus delphis) and stripped dolphins (Stenella coeruleoalba ) (dos Santos et al. 2016, Jefferson et al. 2015).
Habitat Use: There are two distinct geographical forms of the Atlantic spotted dolphin. One of them is larger, has more spots and inhabit mainly along the continental shelf in warmer waters. The other form is smaller, has lighter spots and can be found in deeper areas and around islands such as the Azores (Jefferson et al. 2015).
Acoustics: These dolphins emit about ten different vocalizations as whistles, squawks, barks and buzzes that correspond to different behaviors. In this species whistles are emitted at frequencies between 7 and 16 kHz (Herzing, 1996, Azevedo et al. 2010).
Pod Size: Usually moderately sized groups with less than 50 individuals. However in the Azores they can be observed in large groups with hundreds of animals (Jefferson et al. 2015).
Typical Behaviour: These dolphins perform many aerial behaviors and are one the species that most interact with boats in the Azores. They are mainly shallow divers but can dive up to 40-60 m. The pods are generally distributed by gender and age (Jefferson et al. 2015).
Azevedo, A.F., Flach, L., Bisi, T.L., Andrade, L.G., Dorneles, P.R., & Lailson-Brito, J. (2010). Whistles emitted by Atlantic spotted dolphins (Stenella frontalis) in southeastern Brazil. The Journal of the Acoustical Society of America 127, pp. 2646–2651. doi:10.1121/1.3308469.
Dos Santos, R.P, Simião, S., Madruga, P., Mendonça, A.S., Seitre, R. & Pereira, J.N.G. (2016). Anomalously White Atlantic Spotted Dolphins (Stenella frontalis, Cuvier, 1892) Off the Azores. Aquatic Mammals 42, pp. 244-252. doi: 10.1578/AM.42.2.2016.244.
Herzing, D.L. (1996). Vocalizations and associated underwater behavior of free-ranging Atlantic spotted dolphins, Stenella frontalis and bottlenose dolphins, Tursiops truncatus. Aquatic Mammals 22, pp. 61-79.
Jefferson, T.A., Webber, M.A., Pitman, R.L. (2015). Marine Mammals of the World; A Comprehensive Guide of Their Identification. 2nd edition. London: El Sevier.