Body weight as an effective tool for determination of onset of puberty in captive female Nile hippopotami (Hippopotamus amphibious)

Abstract

Modern humans exhibit increasing relative enamel thickness from M1 to M3. Some biomechanical (basic lever) models predict that the more distal molars in humans encounter higher occlusal forces, and it has been postulated that this provides a functional explanation for the observed gradient in relative enamel thickness. However, constrained three‐dimensional models and experimental observations suggest that there is a reduction in bite force potential from M1 to M3, which would be consistent with the tendency for humans to reduce the size of the distal molars. In this regard, it has been postulated that the distal increase in enamel thickness is a consequence of crown size reduction; thus, it is unnecessary to invoke functional scenarios to explain this phenomenon. We assess these competing proposals by examining relative enamel thickness in a catarrhine primate (Papio ursinus) that exhibits crown size increase from M1 to M3. The molar row of P. ursinus is positioned relatively far forward of the temporomandibular joint, which results in the baboon being able to exert relatively greater muscle forces during posterior biting in comparison to modern humans. Thus, a significant distalward gradient of increasing enamel thickness would be expected in P. ursinus according to the hypothesis that posits it to be functionally related to bite force. The present study reveals no significant difference in relative enamel thickness along the molar row in P. ursinus. This finding lends support to the notion that the relatively thicker enamel of human distal molars is related primarily to their reduction in size. This carries potential implications for the interpretation of enamel thickness in phylogenetic reconstructions: the relatively thick molar enamel shared by modern humans and some of our fossil relatives may not be strictly homologous, in that it may result from different underlying developmental mechanisms. Am J Phys Anthropol, 2005. © 2005 Wiley‐Liss, Inc.

Hippopotamidae (Hippopotamus)

“…74 An enzyme immunoassay to determine progestagens in feces and serum is available. The vulva is difficult to visualize, as it lies hidden in the perineal folds.…”

“…The common hippo reproduces well in captivity. 23,24,49,74,75 Contraception of the female hippo is possible with the use of synthetic progestins such as melengestrol acetate (MGA) in the feed. Gestation lasts 240 days, and postpartum estrus in this species contributes to very short intercalving periods of 1.5 to 2 years.…”

Urinary steroid hormone analysis of ovarian cycles and pregnancy in mandrills (Mandrillus sphinx) indicate that menses, copulatory behavior, sexual swellings and reproductive condition are associated with changing estrone conjugates (E1C) and pregnanediol‐3‐glucuronide (PdG)

“…All samples were analyzed at a dilution of 1:20, 1:40 or 1:80. Individual baseline hormone concentrations were determined by iterative process previously described in Wheaton et al [2006].…”

Suppression of ovulation in Nile Hippopotamus (Hippopotamus amphibious) using melengestrol acetate‐treated feed or high dose Depo‐Provera injection

“…The Nile hippopotamus is a species that matures rapidly [Wheaton et al, 2006] with accelerated reproduction and a short gestation period relative to other large megaherbivores [Owen-Smith and Norman, 1998;Eltringham, 1999;Graham et al, 2002a]. Hippos breed easily in captivity and a lengthy period of lactational anestrus is rare.…”

“…Pregnancies last approximately 240 days [Miller, 2003] and are characterized by sustained elevations in fecal progestogens that are more than double the concentration observed during the luteal phase [Graham et al, 2002a]. In captivity, hippos are reproductively mature by 3 years of age [Wheaton et al, 2006] and have a long lifespan of 40 years. It is estimated that hippos have the reproductive capacity to produce up to 25 young in their lifetime [Owen-Smith and Norman, 1998].…”