472 Natural Resources Systems Copyright Goodheart-Willcox Co., Inc. Reproduction Rate Reproduction rates can be a contributing factor to a species’ extinction, especially when there is a low number of specimens available for breeding. In some species, such as domesticated cats (Felis catus), the reproduction rate is high because the females can carry offspring at an early age (4 to 6 months old), have a short gestation period (58 to 67 days), and can have large litters that are weaned quickly (4 to 6 weeks). Other species, such as dolphins, have low repro- duction rates because it takes 5 to 13 years for the female to reach maturity and they have long gestation periods (12 months). Dolphins nurse their young for about two years and are unlikely to have more than one calf at a time. See Figure 19-9. The long span of time required for maturity and gestation in some species builds a population slowly. If members of the population are dying quickly because of disease, habitat loss, or overhunting, the species cannot reproduce quickly enough to sustain the population. Minimum Viable Population The minimum viable population (MVP) of a species is the lowest number of individuals needed for the species to survive in the wild. Scientists have attempted to establish an MVP that can be applied to numerous species but research indicates that the MVP estimate differs among species because of fac- tors such as different habitat requirements and reproductive rates. One factor that applies to different species is that the MVP must be high enough to pre- vent inbreeding and maintain genetic diversity. Elephants have the longest gestation period of all mammals. An elephant’s gestation is about 22 months or 640 to 660 days. Did You Know? FLICKETTI/Shutterstock.com Figure 19-9. Domestic cats often have large litters that can be weaned by six weeks. Dolphins, however, typically have one cub that they nurse for around two years. How does a longer gestation period affect an endangered species? Azami Adiputera/Shutterstock.com