Response of diademed sifaka (Propithecus diadema) to fosa (Cryptoprocta ferox) predation in the Betampona Strict Nature Reserve, Madagascar.

Large-bodied mammals living in fragmented habitats are at higher risk of extinction, and such risk can be influenced by ecological factors such as predator-prey system dynamics. These dynamics can be particularly complex for conservation management when one endangered species preys on another endangered species in an isolated or poor-quality habitat. Here we describe predation events observed over 19 months that involved two threatened species: the largest carnivore in Madagascar, the fosa (Cryptoprocta ferox), and three groups of diademed sifaka (Propithecus diadema) in the Betampona Strict Nature Reserve. This site is a 22 km2 low-altitude rainforest that is surrounded by agricultural land and isolated from larger forest corridors. We aim to (1) assess the behavioral changes of P. diadema in response to fosa attacks and identify any antipredator strategies that they adopted, and (2) quantify the frequency of fosa attacks and the predation impact on the sifaka population. We report five direct observations of fosa predation attempts (one successful), the discovery of a dead sifaka with evidence of fosa predation, and the disappearance of three individuals. We describe the observed attacks and compare the sifaka activity budgets and movement patterns before and after the events. To escape the predator, sifakas fled short distances, hid, and remained vigilant. The impact of predation, combined with low reproductive rates and potentially high inbreeding of this isolated diademed sifaka population, could affect the survival of this species in Betampona. Given the compounding effects of habitat isolation and high hunting pressure, community-specific conservation strategies should incorporate predator-prey dynamics via longitudinal monitoring of predator and prey population densities and quantifying the predation pressure between them.

Phylogenetic relationships among Indriidae (Primates, Strepsirhini) inferred from highly repeated DNA band patterns.

Comparative studies of highly repeated DNA from different species of Indriidae (Primates, Strepsirhini) allowed confirmation of the specific status of Avahi occidentalis, A. laniger and Propithecus tattersalli. The comparison of their band patterns revealed the existence of specific and common bands from which a cladogram of the family is inferred. This cladogram shows that Avahi clade is the sister-group of Indri and Propithecus clade, and that P. verreauxi is related to P. diadema. These results were discussed in view of those obtained from cytogenetic, morphological and molecular data (mitochondrial DNA). This study shows the capacity of the repeated sequence pattern comparison to be used as a tool for confirming taxa status, (taxinomic classification is a primary determinant of management priorities for endangered species, neglect of distinct taxa may lead to their extinction), and for inferring phylogenetic relationships among related species.

Growth hormone (GH)-releasing hormone secretion is stimulated by a new GH-releasing hexapeptide in sheep.

The acute effect of a new GH-releasing peptide, hexarelin (1 mg, iv), on GH secretion and the mechanisms involved in its changes were investigated in conscious sheep. Peripheral GH levels and GH-releasing hormone (GHRH) and somatostatin concentrations in hypophysial portal blood were measured in six rams. An increase in jugular GH levels was observed 15 min after hexarelin injection (9.1 +/- 1.8 vs. 3.9 +/- 0.8 ng/ml; P < 0.05). This was associated with a stimulation of GHRH release into hypophysial portal blood (145.4 +/- 19.9 vs. 59.2 +/- 10.8 pg/ml; P < 0.01) without a change in somatostatin secretion. Our data indicate that GH-releasing peptide-induced GH stimulation in the sheep involves an activation of GHRH neurons in addition to the previously demonstrated direct effect on the pituitary cells.

Role of growth hormone (GH)-releasing hormone and somatostatin in the mediation of clonidine-induced GH release in sheep.

GH secretion is stimulated by the administration of an alpha 2-adrenergic agonist, clonidine, in several species, including man. This action is probably mediated at the level of the hypothalamus, where the drug may act through inhibition of somatostatin (SRIH) and/or stimulation of GH-releasing hormone (GHRH) release. We have investigated the mode and site of action of clonidine in sheep, because it is possible to collect hypophysial portal blood for the simultaneous determination of GHRH and SRIH in this species under conscious unstressed conditions. Clonidine injection (0.3 mg, iv) resulted in a significant, immediate, and short-lasting (30-min) increase in peripheral GH (14.4 +/- 3.1 vs. 4.8 +/- 1.1 ng/ml; P < 0.01) and portal GHRH (2.7 +/- 0.5 vs. 1.0 +/- 0.2 pg/min; P < 0.01) levels. No change in SRIH secretion was recorded during the same period. Next, we tested the effect of clonidine in sheep actively immunized against GHRH or SRIH. The alpha 2-adrenergic agonist did not affect GH secretion in the anti-GHRH group, whereas immunization against SRIH did not modify the GH response. Finally, we observed that clonidine did not influence GH release from cultured ovine pituitary cells. These data suggest that clonidine acts centrally to stimulate hypophysial GH secretion in the sheep and that this effect is mediated through changes in GHRH, but not SRIH, release into hypophysial portal blood.