imal quickly attracts predators, putting all 

 at risk. Thus, disputes over mating or for- 

 aging are best resolved by wrestling or 

 other forms of bloodless combat. Some 

 deer and antelopes evolved antlers and 

 horns that functioned as shields to parry an 

 opponent's attack and as grappling hooks 

 to wrestle with rivals. Simultaneously, 

 antlers became the focus of mate selection 

 by females, since they advertised a male's 

 superior health and strength. As with the 

 peacock's tail, sexual selection helped 

 make antlers increasingly complex. 



Both stabbing and wrestling horns 

 evolved not only among males but also in 

 the females of some species. In every case, 

 the female's horns mimic those of the age- 

 class of males that she must confront and 

 defeat. In reindeer, for instance, females 

 most often clash with two-year-old males, 

 which — unlike older males — retain their 

 antlers long after the rut. When females 

 dig deep craters in the snow to reach 

 buried lichens, they must frequently de- 

 fend their cosdy efforts from young males 

 that try to steal the food. In woodland cari- 

 bou, however, which feed mainly on arbo- 

 real lichens, females rarely grow antlers. 



Because we have a fairly complete fos- 

 sil record of Old World deer irom the mid- 

 Tertiary onward, this group best illustrates 

 the evolutionary sequence of ander forms. 

 And for each type, one also finds a 

 palmated version (as in moose) and one 



with extra "twigs" branching off the main 

 tines. Moreover, virtually every type of 

 antler that has ever evolved is still repre- 

 sented in living species. 



The first true deer resembled the small, 

 antlerless ruminants from which they 

 evolved. The water deer of Korea and 

 China, with its long, tusklike canines, rep- 

 resents this stage today. Deer with both 

 long, sharp upper canines and small 

 antlers represent the second stage. A 

 plethora of muntjac species in Asia's trop- 

 ical and subtropical forests are similar to 

 this ancient type, which goes back about 

 twenty million years. Muntjacs hold down 

 territories, and males use both antlers and 

 teeth in combat. Three-pronged antlers 

 arose within the deer lineage during the 

 Pliocene in southern Eurasia. Upper ca- 

 nines regressed or disappeared in adults. 

 Today, such deer species remain in tropi- 

 cal southern Asia and fill many ecological 

 niches. They range from the very large 

 sambar, a coarse-grass feeder, to the small 

 hog deer and its island relatives. None are 

 territorial. 



Sociality increased in tandem with four- 

 pronged antlers, which evolved during the 

 late Pliocene in wann temperate climates 

 at the beginning of some two dozen 

 100,000-year cooling cycles. Modem rep- 

 resentatives of this group include the gre- 

 garious sika and fallow deer, both from 

 temperate zones. Five-pronged antlers ap- 



peared in cool climates in the early ice 

 ages. These gregarious ungulates are ex- 

 emplified today by the red deer and its 

 many subspecies. Also during the ice 

 ages, the closely related six-pronged 

 North American elk appeared. 



On the vast expanses of open terrain 

 during the ice ages, a number of very large 

 deer appeared: the large-antlered giants, 

 such as the Irish elk and its relatives; the 

 "brush-antlered" deer; and — in the New 

 World — the large-antlered moose and 

 caribou. In the Southern Hemisphere, 

 antlers reached their largest size in the ex- 

 tinct deer from the Patagonian steppes. 



At high latitudes, the deer enjoy a "va- 

 cation from want" in early summer, when 

 plant food abounds and antlers can grow 

 large without much risk or effort on the an- 

 imal's part. Tropical deer have no such 

 seasonal riches. Beyond sixty-five degrees 

 north latitude, however, the summer boom 

 in vegetation is much too brief to offset the 

 long winter's scarcity of food. Antler size 

 generally increases with latitude and alti- 

 tude, with the trend reversing in the high- 

 est latitudes. Thus, the Tibetan white- 

 lipped deer from the subalpine above 

 timberline carries very large, elklike 

 antlers. The sambar from the tropics, its 

 rival in body size, does not. 



Even when rich habitat permits the lux- 

 ury of large antlers and horns, vigorous 

 males take risks — sometimes skirting 

 predators — to get the very best food for in- 

 creasing antler and body size. Large, sym- 

 metrical horns are visible proof of superior 

 ability at foraging and efficiency in main- 

 tenance metabolism, and they proclaim 

 the bearer's skill at avoiding predators {see 

 "A Consequence of Togetherness," Nat- 

 ural Histoiy, October 1967). 



Large horns among males also appear 

 in other species that live in open habitats, 

 where the deer are under threat from pre- 

 dation. Here the young run with the fe- 

 male, so they must be well developed at 

 birth and grow rapidly. A mother needs to 

 be a fast runner and to excel at obtaining 

 nutrients and converting them to rich, 

 plentiful milk. Today's caribou, which 

 have the largest relative antler mass of any 

 living deer, also have a very showy ander 

 display during courtship, the richest milk, 

 and the most highly developed young at 

 birth among the whole deer family. When 

 a female picks a mate with large antlers 

 under these conditions, she is choosing an 

 individual that may pass on to her daugh- 

 ter the traits necessary for superior lacta- 

 tion and for protecting young. 



Everyone curious about horns has mar- 



67 



