Craniometric study of allometry, adaptation and hybridism of red deer (Cervus elaphus Scoticus, L.) and wapiti (C. e. nelsoni, Bailey) in Fiordland, New Zealand.
- Protection Forestry Division, Forest Research Institute, New Zealand Forest Service, Christchurch
Red deer and wapiti are sympatric in part of Fiordland National Park. Caughley (1971a), on the basis of Fisher's Discriminant Function of 22 skull measurements divided the mixed population of the eastern catchments into 38 % red deer, 20% hybrids and 42 % wapiti.
The same skulls were re-examined with 15 measurements, and re-evaluated against red deer from South Westland, wapiti from Montana and Canada, and further samples from the mixed population area. Separation was based on a polythetic agglomerative cluster analysis, and by comparing groups so shown with those indicated by step-wise 3-group discriminant analysis, 2-group discriminant analysis, and matching of length of skulls. The sample was concluded to comprise only 8% red deer, 52% hybrids and 40% wapiti. The use of North American specimens as controls was dismissed as invalid because they are larger and exhibit different patterns of growth to animals in Fiordland.
The Wapiti Area population is in poor physical condition. The wapiti show, compared with American conspecifics, proportionally high priority for growth of the neurocranium and maxillary region, and slower growth of the viscerocranium. Non-linear changes of most of the cranial bones, compared with length, show that growth occurs in well defined stanzas whereby from three to five years it is concentrated on length characters, after which the skull proportionally broadens. These changes of shape, associated with increase in size throughout life, blur the fidelity of discriminant analysis.
Hybridism in this population is attributed principally to dominant wapiti bulls mating with red deer, hybrid and wapiti females and thereby absorbing most of the red deer into a hybrid gene pool. The hybrid group is morphologically bimodal ("red-like hybrid" and "wapiti-like hybrid") and the range of forms is virtually continuous between the two parent species. Dominance of wapiti is probably reinforced by their breeding season being about two weeks earlier than that of red deer. Grouping of these forms by cranial analysis gives diagnoses which are highly correlated with morphological descriptions of type based on pelage, size and other external characteristics. Consistent with this result, culling of red deer and hybrids by experienced hunters is highly selective