LEPORIDiE 163 



the Brown Hare and the Rabbit has not been demonstrated, 

 and, even if present, they are certainly not conspicuous. 



There are two annual moults in all northern forms, and the 

 colour-changes which accompany them may be more or less 

 conspicuous according to the climate. Many forms are white 

 in winter, but dusky or brown in summer, and the change of 

 colour may affect both the hairs and the underfur, or only the 

 hairs ; others (including Orydolagus) undergo only a partial 

 whitening in winter. Southern forms do not whiten at all, and 

 in some cases, as in the American subgenus Macrotolagus, which 

 includes the Black - tailed Jack Rabbits of Mexico and the 

 Western United States, there is only one moult, usually in 

 late summer or autumn. Individuals of the same species may 

 at different parts of their range exhibit all the different 

 steps between complete winter whitening and the opposite 

 condition ; this being the case with L. europceus, and almost so 

 with the American White- tailed Rabbit or Prairie Hare 

 (Z. campestris). A feature of the moulting period is the 

 falling out of the old dead hairs in blocks so as to expose 

 the underfur and temporarily alter the colour of the animal. 

 Similarly, unexpected colour effects are produced by the wearing 

 away of the black tips of the hairs and by bleaching, but the 

 latter process is not conspicuous in British hares. In addition 

 to the regular moults, many of the hairs may be cast and 

 replaced at any season of the year. 



The colour is evidently very plastic and liable to be 

 influenced by climate ; species inhabiting deserts are paler and 

 greyer, while those of humid regions are darker and have the 

 buff or rusty shades deeper and richer. The arctic hares of 

 America are tricoloured, with the flanks darker than the back ; 

 but other American species have the sides lighter, and in the 

 White-sided Jack Rabbits of the Lepus callotis group the con- 

 spicuous white flank-area can be shifted at will on to the back, 

 so as to form a directive signal (Nelson, op. cit., 25-26). 



Age characters: — Hares and rabbits grow rapidly and breed 

 at a very early age, even before they are fully grown. It is not 

 easy to distinguish perfectly adult individuals, and inability to 

 do so has led to many mistakes, although careful instructions 

 on this point have been handed down for generations from old 



