BREAKDOWN OF ISOLATION MECHANISMS IN TWO SPECIES OF CAPTIVE JUNGLEFOWL (GALLUS GALLUS AND GALLUS SONNERATII).

Reproductive isolation of two species of junglefowl occurs in parts of India and Pakistan primarily due to different geographic distribution. The Grey junglefowl (Gallus sonneratii) occurs west and southwest of the Godaveri River in scrub jungle associated with a more xeric environment than that found east of the Godaveri. The Red junglefowl (Gallus gallus) is found east of the Godaveri in a series of differing ecological communities which' generally have higher annual rainfall and extensive mixed jungle and grassland areas (Beebe, 1926; Collias and Collias, 1967; Delacour, 1951; Johnson, 1963; Morejohn, pers. observ.). In the headwaters region of the Godaveri the ranges of both species overlap (Baker, 1928). In this region of sympatry there is need for extensive study in the field concerning the nature of the sexual isolation which undoubtedly plays an important role in separation of the two species. What the frequency of contact between the two species is that results in the production of hybrids is unknown, and it would be extremely difficult to determine because of the exceedingly wild nature of both species. Hybridization of G. sonneratii with native domestic fowl, however, in the vicinity of villages has been reported by Beebe (19181922). Reports of hybridization between the Red junglefowl and the Grey junglefowl in captivity are sufficient to indicate that hybrids can be readily produced (see Gray, 1958 for extensive bibliography; Danforth, 1958). The manner by which sexual isolation has been bypassed to produce the hybrids has not been previously elaborated upon. Furthermore, scant accurate information is available on the fertility of these hybrids. Presented herein, therefore, are the methods by which natural breeding (as opposed to artificial insemination) between the two species was effected, and information is provided on the fertility of the hybrids. METHODS The representatives of the Red junglefowl used in this study were originally procured from the California State Game Farm, Chino, California, and from a game bird breeder of Los Angeles, California. The individuals from Chino had been derived from birds originally imported from Siam, the latter from birds imported from India. Individuals of this species reproduced freely, and little difficulty was experienced raising their young, either under natural conditions or in incubators. The individuals of the Grey junglefowl used were raised to maturity from eggs purchased at the St. Helena Game Farm, St. H-elena, California. These birds were derived from birds originally imported from Pakistan. The Grey junglefowl were kept to themselves until grown with no influence of adults of their own species or of the Red junglefowl. They were extremely wild and had to be handled with care. As adults they bred and the hens laid eggs, but it was difficult to hatch the eggs under natural or incubator conditions. The adult Grey hens left to incubate eggs on their own, invariably abandoned the clutch within a week or two of incubation. Under incubator conditions high mortality was experienced with this species immediately prior to and during hatching. It is felt that the requirements of certain conditions of temperature and humidity that produce optimum hatch in domestic fowl and Red junglefowl are