Abstract
This study was conducted to identify the adaptive thermophysiological adjustments of 24 gazelles (15 - 20 kg and 3 - 4 years old) belonging to 2 gazelle species (Gazella gazelles and Gazella leptoceros) for 3 months during both summer and winter seasons. The obtained results indicated that gazelles were exposed to heat stress during the summer season, based on the findings that calculated average temperature-humidity index (THI) prevailed during summer season surpass the THI threshold above which most animals enter a state of severe heat stress. Under these supra-neutral conditions, gazelles of both species had manifested noticeable (P<0.05) changes in their thermophysiological responses as demonstrated by pronounced elevations in rectal and skin temperatures as well as marked reductions in internal, external, and total body thermal gradients compared to the winter season. Notably, the use of body heterothermy by gazelles resulted in heat storage of 109.65 and 31.92 kJ/day/animal in summer and winter, respectively. Dissipation of these amounts of heat by insensible evaporative avenue would require 45.61 and 13.82 ml H2O/day/animal in summer and winter, respectively. Furthermore, exposure of gazelles to hot environmental conditions during the summer season elicited marked (P<0.05) alterations in blood haematological and biochemical parameters as revealed by the reduced (P<0.05) erythrocytic indices, total protein and globulin concentrations as well as the elevated (P<0.05) heterophil/lymphocyte ratio, serum albumin, glucose and haptoglobin concentrations compared to the winter season. These findings collectively prove that gazelles can apply remarkable adaptive thermophysiological adjustments in order to survive the harsh bioclimate at their habitats.