Quick Guide: Long-beaked Common Dolphin

Long-beaked Common Dolphin - Delphinus capensis

Delphinus capensis pair

D. delphis and D. capensis have only recently been recognized as separate species.1 They are very closely related. The two species are not known to form mixed schools.

Sighting Cues: Criss-cross color pattern on sides (muted); high dorsal fin, falcate or tall & triangular. Typically large schools of hundreds; this form is seen less often than its congener.

Size: 6.6-7.7ft (202-235cm) males, 6.3-7.3ft (193-224cm) females

Behavior: Bow riding on mysticete whales; pitch poling, a high vertical leap followed by belly-flop.

Habitat/Range: Warm, shallow waters 20m-180m deep, generally coastal;

Migration: None observed

Reproduction/Life History:

Mating season - unknown

Gestation – 10-11 months

Birth/calving season - unknown

Litter size - unknown

Neonate size - unknown

Age at Weaning – 5-6 months or older

Age at Sexual maturity – 7-12 yrs males, 6-7 yrs females

Lifespan – max ~22 years

Diet: Sardines (Sardinops coerulea), anchovies (Engraulis mordax), sauries (Cololabis saira), small bonitos (Sarda chiliensis), and squids (Loligo opalescens). Diet varies with season and region. Foraging dives to 200m to feed on mesopelagic fishes and squids in deep scattering layer. Feeding habits of D. delphis vs. D. capensis have not been compared.2 There seems to be no obvious difference in the diet between these two species3..

Threats: Tuna purse-seine fisheries; gill nets

IUCN Status: Lower Risk/Least Concern

 

In the southern California waters, stomach content analyses showed that short-beaked common dolphins feed more on squid, a prey usually caught at depth during the day or at surface at night, than do long-beaked common dolphins (Schwartz et al. 1992). Decreased squid abundance during the last two El Nin˜o events (California Department of Fish and Game 2000) could partially explain the greater number of short-beaked

common dolphins before both El Nin˜o events and the decrease in number after

these events.

            Although short-beaked and long-beaked common dolphins were both sighted

in similar locations of the bay, confirming a sympatric micro-range, no occurrence

of these two taxonomically close species in mixed schools was ever observed.

The slight difference in diet could indicate a separation of ecological niches reducing

the occurrence of direct competition for food resources when the dolphins

are sympatric. Different preferences in prey for sympatric dolphins were observed

by other authors (Das et al. 2000; Hale et al. 2000). Gowans and Whitehead

(1995) explained the co-occurrence of species either by a superabundance of food

or by a slightly different diet that may eliminate a competitive pressure between

the species. Ohizumi (1998)

 

1Distinguished morphometrically by Heyning and Perrin (1994), and genetically by Rosel et al. (1994).

2 Stock Assessment Report, SWFSC, NMFS, 2007.

3 Ohizumi H, Yoshioka M, Mori K, Miyazaki N (1998) Stomach contents of common dolphins (Delphinus delphis) in the pelagic western North Pacific. Marine Mammal Science 14:835-844