FISHES 201 



barren-ground caribou (Preble, 1908) and the bison (Seton, 1909, 

 1929). 



Altitudinal migrations occur in all the migratory groups, but the 

 community relations of such movements are best known among the 

 ungulates, especially deer. Russell (1932) has discussed the seasonal 

 migration of the mule deer from high to low altitudes in Yosemite 

 and Yellowstone National Parks; this is governed by snowstorms 

 which operate through covering and rendering food inaccessible. The 

 spring return also is dependent upon forage conditions, which in turn 

 depend upon temperatures. The Kaibab deer leave the coniferous 

 forest of the higher altitudes in the autumn and move, generally in a 

 westerly direction, to the pinyon-cedar belt lower down. The favorite 

 winter browse is cliff rose, with juniper and sage less favored; they 

 less frequently resort to a long list of other woody plants (Rass- 

 mussen, MS 1932). In was recently estimated that 80 per cent of the 

 favorite winter food plants were destroyed by overbrowsing during 

 one of the last cyclic maxima, wlien many deer died of starvation and 

 resulting disorders. When faced by a food shortage (cf. Figs. 41^4, 

 page 186) , this species did not migrate east to accessible districts with 

 much better food supplies, but stayed in the favorite ancestral area to 

 their own detriment, and contrary to the usual assumption as to what 

 always happens when food is scarce. 



Fishes. Recurrent migration appears to be more characteristic 

 of fishes than of any other aquatic group, but emigration is more or 

 less exceptional so far as is known. The former is regularly asso- 

 ciated with spawning and hence involves a marked change from the 

 usual habitat of each species, such as a change from salt to fresh 

 water, or the reverse. Typical of the marine species that move from 

 deep to coastal waters for breeding is the herring, the behavior of 

 which has been described by Meek (1916), and summarized by Heape 

 (1931). The European herring passes the spring breeding period, and 

 the subsequent feeding one, in shallow waters and then retires north- 

 ward into deep water for the quiescent season of winter. The young 

 are said to follow the adults for part of the spring journey for several 

 years, until they too are mature and ready to spawn, thus indicating 

 that instinct is not the guide. Other fish with a more or less similar 

 habit are the mackerel, tarpon, tunny, pilchard, hake, garfish, blue- 

 fish, the sharks, and perhaps the cod. The number of species known 

 to move from coastal to deep waters is much smaller, but among them 

 are the conger eel and swordfish. 



The behavior of anadromous fishes has attracted much attention. 

 If it is assumed that the bony fishes probably originated in fresh 



