1936] Hatt, Hyraxes Collected by American Museum Congo Expedition 137 



an annual cycle of pelage change it is not indicated in this series which 

 contains specimens scattered fairly well over the year. The series can- 

 not be expected to show geographical variation as the three localities 

 represented are close together — about one hundred miles apart in the ex- 

 tremes. 



Attainment of Full Growth 



The smallest specimen in Stage VIII measures 480 mm., the longest 

 585. Of the two specimens in Stage VII, the smaller measures only 

 three mm. less than the smallest in Stage VIII, the larger well within the 

 limits of variation of the above. The single skull in Stage VI is from a 

 specimen longer than either of those in Stage VII, while three in Stage 

 V are from specimens practically within the limits set by the two in 

 Stage VII. The one skull in Stage IV is from a specimen 15 mm. 

 longer than the smallest animal with a Stage VII skull. Two skulls in 

 Stage III are from animals 378 and 382 mm. long. Thus, animals fully 

 adult as measured by the attainment of function of the complete denti- 

 tion range in size between limits that are within five mm. of embracing 

 the range represented by all specimens down to the stage in which the 

 second upper molar is only partly up. Animals in Stage III (M 1 func- 

 tional, M 2 below the level of the bone) are distinctly smaller. It would 

 appear from this that full growth in this species is attained at about the 

 time of the eruption of the second upper molar, which contrasts with the 

 situation suggested by the Congo Expedition collection of tree hyraxes 

 {Dendrohyrax d. emini) where full growth seems not to be attained 

 before the period of full function of the second upper molar (Stage V). 

 The period of time between the eruption and the functioning of M 2 may 

 not be great, however, and actual differences in growth pattern between 

 these two species may be very slight, or even nonexistent, for the series 

 with which I have worked is too small to furnish statistical proof. 



Behavior 

 Notes made by Mr. Lang at Aba, December 18, 1911 are: 



The colonies on these rocky hills are rather small, three or four being the usual 

 number of animals. They are, however, found on every rock, the cracks and boulders 

 of which offer sufficient shelter to them. The largest number found in one colony was 

 fourteen, but in this case the rock is exceptionally large and the hyraxes from the 

 whole rock assemble at one side to bask in the sun. On this rock is a place where the 

 water has collected. The hyraxes evidently wade into the water (about 5 inches 

 deep) to chew off the sprouts of a flowering water plant. 



