Studies on the Two New Zealand Bats
Table I shows the relationship of ear length (from junction with head and from meatus), forearm length, digital length (third metacarpal and associated phalanges) to total length for the eleven specimens of Mystacina available during this study. Comparable date from the literature has been included and where possible the subspecies has been indicated. "Ear length" of Hutton (1872) and Dobson (1878) has been considered equivalent to "ear length from meatus" in the present table. Carter, Hill, and Tate (1946) give measurements for the head and body, for the tail and for the forearm, but these are approximations of Dobson's (1878) values and have not been included here. Values based on ear measurements for D.M. 352 (female) are considered unreliable as the specimen was a skin in poor condition and these structures were somewhat withered.
With the exception of this last specimen the values for ear or forearm length compared with total length fall into two groups corresponding with the known ranges of the two subspecies. Ear length from junction with head as a percentage of total length is above 20% in M. t. tuberculata but below this value in M. t. robusta. The values for ear length from meatus are more distinct, above 25% in the northern subspecies, below 23.5% in M. t. robusta. For the forearm corresponding values are 62.5% and 60%. The relationship between digital length and total length is not so marked. Values for M. t. robusta are generally lower, but Knox's (1872) measurements appear to provide an overlap.
The distinction between the subspecies relates both to overall size and to the relative proportions of exposed parts such as nostrils, ears and limbs. Overall size is greater and the extremities relatively shorter in M. t. robusta than in the northern M. t. tuberculata. Such differences are in accordance with Bergmann's and Allen's page 6rules (Allee, Emerson et. al., 1949) relating to structural modifications induced by temperature. No evidence of a continuous cline along a temperature gradient is apparent from the few specimens available. It is noted by Allee, Emerson et. al., that hibernation may reduce the effect of temperature upon structure in mammals by avoiding exposure of the animals to winter minimum temperatures. It is of interest, therefore, that there is some evidence that Mystacina does not undergo a strict period of hibernation during winter months.
|Specimen||Subsp.||Sex.||T.L.(mm)||Ear from head: T.L.||Ear from meatus: T.L.||Forearm: T.L.||Digit: T.L.|