North American Crane Working Group

 

Date of this Version

1992

Document Type

Article

Citation

Swengel, Scott R. "Sexual Size Dimorphism and Size Indices of Six Species of Captive Cranes at the International Crane Foundation.", In: Stahlecker D. W., ed. 1992. Proceedings of the Sixth North American Crane Workshop, Oct. 3-5, 1991, Regina, Sask. (Grand Island, NE.: North American Crane Working Group, 1992), 151-58.

Comments

Conference co-sponsored by the Canadian Wildlife Service, Saskatchewan Parks and Renewable Resources Department, and the Whooping Crane Conservation Association, Canadian Council. Proceedings used by permission of the North American Crane Working Group.

Abstract

Sexual size dimorphism and size indices in captive cranes were studied to learn dimorphism patterns and size relationships that could be used in the management of captive cranes. In 6 species of captive cranes. Siberian (Grus leucogeranus), eastern sarus (G. antigone sharpir), white-naped (G. vipio), common (G. grus), hooded (G. monacha), and red-crowned (G. japonensis), maIes averaged 14.5-28.5% heavier than femaIes (P < 0.05) in all species. MaIes had longer culmens, tarsi, and wing chords in all species. MaIes had significantly longer culmens (P < 0.05) in 4 of 6 species and had significantly longer tarsi than females (P < 0.05) in 3 of 6 species. Culmen and tarsus lengths both averaged 7% longer in males than females when the 6 species were combined. Wing chord length was not significantly dimorphic (P > 0.05) in any of the 4 species measured (Siberian, white-naped, hooded, and red-crowned cranes), averaging only 1.3 -3.3 % longer in males than in females. Body weight correlated significantly with tarsus length, culmen + tarsus length, and culmen X tarsus length in 5 of 6 species (P < 0.05). Weight covaried significantly with culmen length in 4 species, and with wing length in 1 species (P < 0.05). Sex-specific linear regression models predicted weight from linear measurements more accurately than when both sexes were combined, suggesting differences in body scaling between sexes in some species. The best regression formulae used linear measurements to predict crane weights at the International Crane Foundation (ICF) within 1.2-4.2% of actual weight for 5 of the 6 species. Because ICF cranes weighed more than cranes from 3 other zoos sampled, these regression formulae were poor predictors of crane weights at those zoos. Body weight was the best index of overall size within a site, followed by culmen + tarsus and culmen X tarsus. Culmen + tarsus and culmen x tarsus are probably the best indices of overall size among sites. Wing chord and weight measurements vary over time, so caution should be used when comparing these among individuals. All species gained weight between September and November. Red-crowned and Siberian cranes undergo large fall weight gains and remain heavier than normal all winter. Sexual size dimorphism could be used to determine the sex of some crane species. Using normal weights of cranes may help detect potentially unhealthy weight cbanges (usually losses) in captive or rehabilitated cranes.