Approximately 250 spinner dolphins (Stenella longirostris) live in the lagoon and waters surrounding Midway. The name "spinner" refers to the species' acrobatic displays of leaping and spinning in the air (calves have even been observed trying to spin shortly after being born). Females give birth to one calf, but babysitting is a common practice. Nursing females, other adult females, and even a few males will form nursery groups to increase the safety of calves and teach them important life skills. Pollution in the form of marine debris poses a constant threat of entanglement, especially to young calves. The IUCN Red List reports that this species is currently "data deficient," meaning its conservation status has not yet been determined.