Regional variation in body size of the cheetah (Acinonyx jubatus)

Felidae species show a great diversity in their diet, foraging and hunting strategies, from small to large prey. Whether they belong to solitary or group hunters, the behavior of cats to subdue resisting small or large prey presents crucial differences. It is assumed that pack hunting reduces the per capita risk of each individual. We hypothesize that the sacroiliac articulation plays a key role in stabilizing the predator while subduing and killing prey. Using CT-scan from 59 felid coxal bones, we calculated the angle between both iliac articular surfaces. Correlation of this inter-iliac angle with body size was calculated and ecological stressors were evaluated on inter-iliac angle. Body size significantly influences inter-iliac angle with small cats having a wider angle than big cats. Arboreal species have a significantly larger angle compared to cursorial felids with the smallest value, and to scansorial and terrestrial species with intermediate angles. Felids hunting large prey have a smaller angle than felids hunting small and mixed prey. Within the Panthera lineage, pack hunters (lions) have a larger angle than all other species using solitary hunting strategy. According to the inter-iliac angle, two main groups of felids are determined: (i) predators with an angle of around 40° include small cats (i.e., Felis silvestris, Leopardus wiedii, Leptailurus serval, Lynx Canadensis, L. rufus; median = 43.45°), the only pack-hunting species (i.e., Panthera leo; median = 37.90°), and arboreal cats (i.e., L. wiedii, Neofelis nebulosa; median = 49.05°), (ii) predators with an angle of around 30° include solitary-hunting big cats (i.e., Acinonyx jubatus, P. onca, P. pardus, P. tigris, P. uncia; median = 31.80°). We suggest different pressures of selection to interpret these results. The tightening of the iliac wings around the sacrum probably enhances big cats’ ability for high speed and large prey control. In contrast, pack hunting in lions reduced the selective pressure for large prey.

Download Full-text

The biology of banded (Lagostrophus fasciatus) and rufous (Lagorchestes hirsutus) hare-wallabies (Diprotodontia : Macropodidae) on Dorre and Bernier Islands, Western Australia

Wildlife Research ◽

10.1071/wr99109 ◽

2001 ◽

Vol 28 (3) ◽

pp. 311 ◽

Cited By ~ 5

Author(s):

J. D. Richards ◽

Jeff Short ◽

R. I. T. Prince ◽

J. A. Friend ◽

J. M. Courtenay

Keyword(s):

Body Size ◽

Sexual Dimorphism ◽

Sex Ratio ◽

Body Condition ◽

Regional Variation ◽

Reproductive Age ◽

Island Populations ◽

Shark Bay ◽

Males And Females ◽

Bay Islands

Sex ratio, reproduction, body condition and morphology of banded (Lagostrophus fasciatus) and rufous (Lagorchestes hirsutus) hare-wallabies were assessed on Dorre and Bernier Islands. Data are derived from 236 banded hare-wallabies and 161 rufous hare-wallabies captured between 1959 and 1999. The sex ratio of captured banded hare-wallabies tended to be female-biased (0.79: 1 male: female) but was not a significant departure from parity. In contrast, pouch young tended towards a male bias at 1.35: 1. Females produced 1–2 young per year. They were capable of producing young at 1000 g, but the incidence of females carrying pouch young or lactating increased from 39% for females of 1000–1400 g to 80% for females of 1401–1800 g, then decreased slightly to 76% for females >1800 g. Births occurred throughout the year but there was some indication of a decline in the latter half of the year. Captured banded hare-wallabies ranged in weight from 850 to 2300 g. Animals on Dorre Island were in significantly better body condition than those on Bernier Island, although this could be an artefact of their shorter pes length. There was no evidence of sexual dimorphism and no differences in morphological measurements taken, other than pes length, between the two island populations. The sex ratio of captured rufous hare-wallabies was close to parity at 0.99: 1 and for pouch young tended to be male-biased at 2: 1. The smallest female with young weighed 1215 g, but the incidence of females carrying pouch young or lactating increased from 43% for females of 1215–1660 g to 61% for females of 1661–2015 g and 100% for females >2015 g. Females carried pouch young in all months sampled (March–September) and one incidence of twinning was noted. Captured rufous hare-wallabies weighed 600–2550 g. Body condition was similar for males and females and between islands, but smaller females of reproductive age were in poorer body condition than larger females. There was no evidence of sexual dimorphism but pes lengths of animals on Dorre Island were significantly shorter, head lengths longer and tail lengths shorter, than those on Bernier Island. Rufous hare-wallabies appear to show regional variation in body size, being smaller in the wetter and warmer Tanami/Alice Springs region and larger on the drier and cooler Shark Bay islands.

Download Full-text