343 



KDooiledge & Seleotifle Hems 



A MONTHLY JOURNAL OF SCIENCE. 



Conducted by MAJOR B. BADEN-POWELL, F.R.A.S., and E. S. GREW, 



M.A. 



Vol. III. No. 15. 



[new series.] 



FEBRUARY, 1906. 



SIXPENCE NET. 



CONTENTS- See page VII. 



TKe ColoroLtion of 

 MaLminaLls ©Liid Birds. 



By J. Lewis Bo.nhote, M.A., F.L.S., F.Z.S., M.B.O.U., etc. 



(Cimtinucd from page 317.) 

 Let us now consider for a moment the question of 

 those mammals whose pelage changes at certain seasons 

 of the year. 



Roughly speaking, in the tropics, the wet and dry 

 seasons correspond to- our summer and winter, so that, 

 if an animal is to be at all affected by the climate, the 

 affection will show itself, roughly speaking, in spring 

 and autumn, at the same time, approximately, as when 

 the cold or heat are affecting the animals of more 

 northern climes. 



Mr. Lydekker, in an article in the Field,* points out 

 that Scinriis caniceps was the only tropical mammal 

 that, to his knowledge, had a seasonal change. This 

 particular squirrel, in company with another, .S. 

 airpdorsalis, assumes in mid-winter a very bright or 

 intense coloration on the back, which, as I have pointed 

 out| some years ago, is caused by the advent of sexual 

 activity, and not by any climatic or seasonal change. 

 The climate at that time of year (December to February) 

 is very constant, and this is, therefore, a clear instance 

 of a change being brought about solely by sexual 

 activity. 



On the other hand, we have certain species, such as 

 Sciurus maclellandi, Ftinambulus berdnwrei, etc., in which 

 their season of most intense colouring coincides with 

 the summer or wet period, but in this case the change 

 is merely one of relative brightness and not sO' marked 

 as in the other cases. 



Among birds, the changes seem to be almo.st always 

 " breeding changes " for they take place at the breed- 

 ing season and are probably due almost entirely to 

 sexual causes and impulses, and we would suggest 

 that any changes in the tropics which may take place, 

 as being purely due to seasonal causes, are to be found 

 among the representatives of northern races where the 

 necessity of a change arose and has not yet been eradi- 

 cated. A good example is to be found in ]\/usicla 

 flavigida. This animal, which is of a light brown and 

 yellowish colour in Siberia, has in Nepal a marked 

 seasonal change, becoming much darker in summer. 

 In the Malay Peninsula, although both pelages are 

 darker than those assumed in the North, the seasonal 

 change still persists, while in Java and .Sumatra, the 

 dark brown form is permanent throughout the year. 

 In the Peninsula of India is also found another species 

 {M. gwaikinsi), which is uniformly dark, and has, as 

 far as we know, no seasonal change. 



• Field, 1903, p. 675. 



t P.ZS., igor, p. 



Toi sum up concisely : — 



Conditions of climate being more equable, " changes 

 of pelage " are not so frequent in the tropics as in more 

 northern climes ; when they do occur, they are probably 

 due — 



(i.) Either to the sexual impulses alone, e.g., 



S. caniceps and S. airodorsalis. 

 (2.) Or to a long ingrained habit,* owing to the 

 animal having originally come from some 

 climate where seasonal change was 

 necessary, e.(i., Mustela flavigula, Cervusy 

 and possibly Sciurus. 



TFMPER.A.TE REGIONS. 



After all that has been said on the other regions, 

 there is not much to- note here, except to point out that 

 the arguments for the other regions still hold good. 



In the first place it is fairly self-evident that in most 

 of the mammals and birds of this reg-ion the prevailing 

 coloration is brown; white mammals are as .scarce as 

 they are in the tropics, and bright coloured forms be- 

 long, without exception, to tropical or cosmopolitan 

 families. The squirrel and the fox are good instances 

 of mammals that have partially retained their bright 

 colour, the former during summer only, the latter 

 throughout the year; the deer also are red in summer. 



The birds also call for little comment on these lines. 

 The bright species, as the kingfisher and roller, being 

 typical of the tropics, and the SylviidEB, or warblers, 

 typically birds of the temperate region, are brown. 



The chief interest of the temperate region, however, 

 lies in those families that, stretching from the north 

 and even penetrating the Arctic circle, mav also be 

 found on the northern edge of the tropics, becoming 

 brighter and brighter gradually and throughout the 

 whole distance as they approach the southern limit of 

 their range. 



More heat, better and more abundant food, more 

 time between the periodic breeding season and the cold 

 of winter, or the gentle advent of sprintr. all these are 

 causes which, as we have shown, may and do affect the 

 '" vigour " of the indi\idual, and it is bv means of 

 that " vigour " and not by their direct action that we 

 suggest the brighter colours are produced. 



• It is not advisable to press matters too minutely in a general 

 paper, but it is perhaps worthy of note that in Conns clJi. an 

 inhabitant of Burma, Malay Peninsula and Cochin China, the 

 brightest pelage is that assumed and worn in winter, and is 

 tlierefore hardly analogous to the ch.inges in C. ileawiceli, whose 

 brightest phase is in summer, I would therefore suggest that the 

 change in C. cldi is purely a breeding change and that it has 

 progressed a stage further than C. axis and C. iwicolor, that have 

 ,1 s'milar pe'age throughout the ye.ir, in having tirst eliminated 

 the seasonal change and then adopted the breeding change ; 

 this would merely depend on the balance between the sexual 

 and climatic impulses. 



t For a further instance of the seasonal change pesisting under 

 altered conditions, see Captain Barrett-Ham'lton. P.Z.S., i8og — 



P- 59^- (7o he continued.) 



