Aggressive behaviour in immature captive Nile crocodiles, Crocodylus niloticus, in relation to feeding

Reference levels for corticosterone and immune function in farmed saltwater crocodiles (Crocodylus porosus) hatchlings using current Code of Practice guidelines

“…Secondly, the biomass of animals within each pen was highest at Sampling 2 and animal numbers were subsequently reduced thereafter. Elsey et al (1990a) reported higher CORT with higher stocking densities in juvenile American alligators and while the number of animals within the pens had not changed, the animals had grown significantly so again the competition for resources had increased (Morpurgo et al, 1993). Lastly, as mentioned above, there is also the possibility that sampling error or unaccounted stressors specific to Sampling 2 may have contributed to increased CORT values although the former seems unlikely as efforts were made to standardise sampling methods employed at each period.…”

“…Firstly, previous studies have illustrated that CORT can be influenced by environment (Romero, 2002;Turton et al, 1997;Tyrrell and Cree, 1998) and Sampling 2 (September/October) coincided with the onset of ''the build-up'', a time of high temperatures and humidity but little to no rain (Webb et al, 1991). Despite the water temperature being thermostatically-controlled (32°C), the rise in air temperature and humidity may have increased metabolic rates inducing greater competition for food and space (Morpurgo et al, 1993). Secondly, the biomass of animals within each pen was highest at Sampling 2 and animal numbers were subsequently reduced thereafter.…”

“…Grading is an essential component of crocodile farming to reduce the size variation within a pen and reduce competition for resources to facilitate growth (Brien et al, 2013;Morpurgo et al, 1993). Since this study was designed to understand the baseline CORT and immune values using current husbandry practices, we necessarily graded animals when necessary based on size and not by randomisation.…”

“…The remaining crocodiles in Shed 1 were dispersed between the empty pens to reduce their stocking densities. Throughout the study period, crocodiles were ''graded'' between pens to minimise the size variation and agonistic interactions (Morpurgo et al, 1993).…”

Nuclear organization and morphology of serotonergic neurons in the brain of the Nile crocodile, Crocodylus niloticus

“…A series of studies in a reptile, Anolis carolinensis, have shown that for this lizard the serotonergic system is involved in the modulation of aggressive social interactions and is modulated by social signals (Summers and Greenberg, 1995;Summers et al, 1997Summers et al, , 1998Summers et al, , 2003aSummers et al, ,b, 2005aEmerson et al, 2000;Korzan et al, 2000Korzan et al, , 2001Larson and Summers, 2001;Summers, 2001;Korzan and Summers, 2004). Given the important role serotonin plays in the mediation of aggression and sociality in Anolis, it is of interest to establish a baseline comparative anatomical description for this system in the brain of the Nile crocodile, a reptilian species that also demonstrates social hierarchies and significant aggressive behaviour (Morpurgo et al, 1993).…”