RETREAT 367 



bourhood. Such a warning is, of course, given unconsciously and 

 is quite on a different footing from the stamping above mentioned, 

 which one must presume is meant by the giver to indicate the 

 approach of danger to his fellows. 



Another burrowing rodent which lives in communities is the 

 Prairie- Dog (Cynomys Ludovicianus) of the western prairies of 

 North America. It is asserted by several observers that in this 

 case sentinels are regularly set for the common good. 



Burrowing animals surprised by enemies when at some dis- 

 tance from their homes commonly attempt, with more or less 

 success, to take refuge in the ground. Of this a notable example 

 is the Small Armadillo (Dasypus minutus] of South America, 

 which, when overtaken by a horseman, is said, if the soil is 

 favourable, to be able to burrow a safe distance into the ground 

 before its pursuer has time to dismount, unless he literally falls 

 off his horse. 



Arboreal mammals, if surprised on the ground, naturally take 

 to the trees if they have the chance, and they may do this in a 

 very cunning way. If, for instance, an ordinary Squirrel (Sciurus 

 vulgaris) (fig. 508), surprised in the act of feeding upon fallen 

 cones or beech-mast, be hotly pursued, it will naturally make for 

 the nearest tree, which it will ascend with great rapidity, always 

 taking the greatest care to direct its flight so that the trunk or 

 branches intervene between itself and the aggressor. It has 

 also been suggested that the squirrel's brush is not only a means 

 of balancing, but also helps escape from carnivorous enemies 

 which, attacking from behind, may at the last moment have to 

 be content with a mouthful of fur. Possibly also, though this is 

 mere conjecture, the delicate and easily -detached tail of the 

 Dormouse (Muscardinus avellanarius] may serve as a kind of 

 sop to the foe, on the principle which has before now led to the 

 escape of sledge-travellers from pursuing wolves, which have 

 checked their pace in order to investigate articles of clothing and 

 other objects thrown out for their inspection. 



Aquatic mammals in retreat of course take to the water if 

 they get a chance, and some terrestrial forms, such as Deer and 

 Kangaroos, select the water in order to make a last stand against 

 dogs, seeming to realize that attack is thus made more difficult. 



Birds in Retreat. Among the large Running Birds are forms, 

 like the African Ostrich, in which the absence of powers of flight 



