Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

2017 - 20182

Settings

Has files: YesSubject: search.filters.subject.Kororā

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The development of the corticosterone stress response of kororā (little penguin, Eudyptula minor) chicks in response to frequent handling : a thesis presented in partial fulfilment of the requirements of the degree of Master of Science in Physiology at Massey University
    (Massey University, 2018) Ogle, Shelley
    In birds, when a stressor is encountered, the hypothalamo-pitiutary-adrenal (HPA) axis is activated to produce the corticosteroid, corticosterone. The production of this hormone incites a flight or fight response in order to best avoid long-term damage from the stressor. However, prolonged or repeated exposure to high levels of corticosterone can have damaging behavioural and physiological effects. For this reason, high levels of the hormone should be avoided where possible in developing chicks. Chicks of altricial species in particular, seldom hatch with a highly functioning HPA axis so as to avoid these detrimental effects while their parents are still protecting them from major stressors such as predators, adverse weather and low food availability. Previously, studies have mapped the development of the HPA axis in a range of species or studied the effects of stress from a young age on future behavioural or physiological responses. This current study aimed to not only describe any adverse effects observed as a result of increased encounters with stressors but also track the development of the HPA axis in kororā (little penguin, Eudyptula minor) chicks. Kororā chicks from the Oamaru Blue Penguin Colony were selected from both available sites and grouped based on their age at the time of sampling, 2 weeks old, 4 weeks old and 6 weeks old and a further two groups were formed for chicks that were handled twice a week from 2 weeks of age until 4 weeks or 6 weeks at which point they were sampled. Blood sampling and handling and capture stress responses were done following a modified standard protocol of a blood sample at 0 mins, 15 mins and 30 mins at which point they were returned to their nest to avoid over or under heating depending on the age and weather. The chicks being exposed to frequent human interactions were weighed twice a week and also had their flipper length and beak width, length and depth measured to graph the growth rates and body condition indices which has never previously been done in penguin chicks. It was found that frequent interactions with people did not have a significant effect on the stress responses when comparing previously handled chicks with unhandled chicks of the same age and that the previously handled chicks developed their adult-like stress response at a similar age to those that had not been previously handled. With regards to body condition indices and growth rates, this study showed that the parents leave the nest just after body condition indices drop to the low point in the chicks’ development.
  • Thumbnail Image
    Item
    The time course of corticosterone responses in kororā (little penguin, Eudyptula minor) : a thesis presented in partial fulfilment of the requirements of the degree of Master of Science in Zoology at Massey University
    (Massey University, 2017) Long, Kar Hui
    When birds and other vertebrates perceive a situation to be threatening the hypothalamopituitary-adrenal (HPA) axis is activated and glucocorticoid hormones are secreted from the adrenal gland. Activation of the HPA axis in response to a stimulus perceived to be threatening is called a stress response. The main glucocorticoid hormone in birds is corticosterone. Corticosterone responses of birds are typically measured by the collection of an initial blood sample when a bird is captured or picked up, then the collection of further blood samples until 30 to 60 minutes has elapsed, at which time the bird is released. Whilst this standard sampling protocol provides information on the size of the corticosterone response, it does not provide any indication of how long it takes for corticosterone concentrations to return to initial values. The main objective of this thesis was to characterise the total duration of the corticosterone response of free-living kororā (little penguins, Eudyptula minor). Little penguins at Oamaru were picked up from their nestboxes and initial blood samples collected. Birds were handled and then restrained by being placed in a box. Further blood samples were collected 15, 30 and 60 min after the birds were first picked up. Birds were then returned to their nest boxes and an additional blood sample collected 15, 30, 60, 120, 240, or 360 min later. Mean corticosterone concentrations declined to initial values two hours after birds were returned to nest boxes. The rates at which corticosterone concentrations increased when a stressor was present and then decreased when the stressor was no longer present were positively correlated. Seasonal changes in corticosterone responses in little penguins were also investigated in this study. Mean corticosterone responses were similar in winter and in the pre-laying period, whereas mean responses were lower in birds during early chick rearing. Corticosterone responses during the pre-laying period were greater in male than female little penguins. The current study is the first to document the complete corticosterone responses of free-living penguins and provides information about changes of corticosterone concentrations after a stressor is removed from the free-living individuals. It is also the first to reveal that free-living penguins with relatively high corticosterone responses to a stressor had relatively high rates of corticosterone decline.