Sexual Dimorphism in Size, Relative Size of Testes, and Mating Systems in North American Voles

1990 ◽  
Vol 71 (4) ◽  
pp. 510-519 ◽  
Author(s):  
E. J. Heske ◽  
R. S. Ostfeld
The Auk ◽  
1966 ◽  
Vol 83 (3) ◽  
pp. 423-436 ◽  
Author(s):  
Robert W. Storer

1999 ◽  
Vol 77 (7) ◽  
pp. 1064-1074 ◽  
Author(s):  
Andrew N Iwaniuk ◽  
Sergio M Pellis ◽  
Ian Q Whishaw

We tested the validity of previously described relationships between forelimb structure and behaviour in mammals by measuring the forelimbs of 22 species of North American carnivores. Nine ratios were calculated from these measurements and made independent of the effects of allometry and phylogeny through the use of log-transformed regressions and independent contrasts analysis. The ratios were then directly compared with two behavioural traits: arboreal locomotion and vertebrate predation. Only five of the nine ratios exhibited a significant relationship with arboreal locomotion and three with vertebrate predation. It was concluded that the brachial index, relative size of the olecranon process, and total forelimb robusticity may be reliable predictors of arboreal locomotion, and that the brachial index, relative size of the olecranon process, and radial robusticity may be accurate predictors of vertebrate predation. The data also suggest that the morphology of the lower forelimb may be an important indicator of prey-capture and feeding behaviour in carnivores and could be used in conjunction with craniodental variables to extrapolate predatory behaviour of extinct species.


1983 ◽  
Vol 40 (11) ◽  
pp. 2019-2024 ◽  
Author(s):  
Terry D. Beacham ◽  
Clyde B. Murray

Male adipose fins of Oncorhynchus species were 30–50% larger than those of same-sized females, the actual amount depending on the species. Accuracy of classification of the standards ranged from 87% in chinook salmon (O. tshawytscha) to 98% in pink salmon (O. gorbuscha). Testing the method on new samples usually resulted in an accuracy of at least 90% correct identification of sex for any species. Relative size of the adipose fin should allow for easy and accurate external identification of the sexes of silver-bright Oncorhynchus.


2001 ◽  
Vol 79 (5) ◽  
pp. 759-765 ◽  
Author(s):  
Andrew N Iwaniuk

A possible relationship between sexual dimorphism in brain size and mating system was investigated in five ground squirrel species: Spermophilus lateralis, S. tridecemlineatus, S. richardsonii, S. columbianus, and S. parryii. Relative brain size was measured by determining the endocranial volume of 247 ground squirrel skulls and regressing these values against two measurements of body size: mass and length. Analyses of covariation in the brain size / body size relationship within the five species revealed that sexual brain-size dimorphism occurs in three of the five species: S. lateralis, S. richardsonii, and S. tridecemlineatus. Application of a reduced major axis regression model indicated, however, that only S. lateralis and S. richardsonii exhibit significant sexual brain-size dimorphism. These findings suggest that the degree of sexual brain-size dimorphism is not directly correlated with variation in mating systems. Spatial abilities may play a role in the evolution of sexual brain-size dimorphism in ground squirrels, but the spatial requirements of mating systems appear to be insufficient. The possibility of sex differences in cognition, resource competition, and other variables as contributory factors to the evolution of sexual brain-size dimorphism is offered, but detailed knowledge of sex differences in the behaviour of ground squirrels is required to provide a definitive answer.


Ecology ◽  
1966 ◽  
Vol 47 (1) ◽  
pp. 143-147 ◽  
Author(s):  
Jared Verner ◽  
Mary F. Willson

1993 ◽  
Vol 74 (1) ◽  
pp. 230-233 ◽  
Author(s):  
R. S. Ostfeld ◽  
E. J. Heske

Sign in / Sign up

Export Citation Format

Share Document