Measuring Penguin Welfare and Stress
by Jemma Dias
Animal welfare has been defined by Broom (1986) as “an animal’s physical and mental state with regards to its ability to cope with its environment”. Animal welfare is a relatively new science, focussing on the quality of our care for captive animals. It is also considered to be an extremely important topic, not only based on our moral responsibility to provide appropriate care for the animals we chose to keep, but also to enhance production, be it for profit or conservation. There is a wealth of factors which affect an animal’s welfare, such as social interaction, diet and overall health. As a result, welfare can fluctuate daily, even hourly, and, therefore, should be monitored regularly. Results from this should lead to alternations in husbandry practices with the aim to improve animal welfare. Welfare assessment can also be applied to wild colonies to assess the influence of environmental change, such as tourism or climate change.
Types of welfare monitoring in penguins (and other animals)
Welfare monitoring for any species can be undertaken in two ways. The first uses behavioural measurements. This requires behavioural observations, as well as an understanding of the individual’s “usual” behaviours. For instance, an increase in abnormal behaviours, such as stereotypes, can indicate significant stress.
Indicators of stress in captive penguins
Other behavioural indicators of stress may include:
- a reduction in activity and subsequent increase in time spent resting
- an increase in aggressive behaviours and decrease in affiliative behaviours towards conspecifics and keeping staff
- poor appetite, but also anticipation of feeding events
- alterations in grooming behaviours, such as excessive grooming
- increased vigilance or avoidance of stressful stimulus
- poor reproductive success, limited interest in mating opportunities and infanticide in some species
- unequal enclosure utilisation limited to a few or even one area of the enclosure, often the area in which food is provided
In penguins, species specific behaviours such as diving, incubating and pair-bonding may also be relevant to welfare assessment. It should also be noted that not all instances of these behaviours should be considered indicative of stress. For instance, occurrences of behaviours, such as grooming, at a particular time of day may be due to weather conditions. Assessment should consider the proportion of time spent performing the behaviour over a full 24-hour period to best understand the cause of a behaviour.
Whilst excessive grooming can be a sign of poor welfare, this Humboldt Penguin at ZSL London Zoo was seen to take breaks between preening.
This Little Penguin at Perth Zoo exhibiting vigilance behaviours on behalf of the rest of the group, who were either preening or swimming at the time.
Sherwen et al. (2015) monitored the effect of zoo visitors on the welfare of 25 Little Penguins using behavioural measures. The penguins’ behaviour was studied in two randomly imposed conditions: enclosure closed to visitors and enclosure open to visitors. The investigation found an increase in intra-group aggression and vigilance in the presence of zoo visitors. The penguins spent a greater period of time positioned behind structural features in the enclosure and chose to stand at a greater distance from viewing areas with visitors present. These results suggest that visitors acted as a stressor for the penguins, likely fear-provoking, indicating welfare is affected by visitors.
Stress in penguins and other birds can be measured in hormones
The results from behavioural welfare assessments can be validated by physiological measures of welfare. The most significant physiological measure of welfare is the presence of stress hormones. Glucocorticoids, such as cortisol and corticosterone, are released into the blood during a stress response. Monitoring the levels of stress hormones can show the occurrence of stress, as well as supporting theories on the cause of stress and instances of stress related behaviour.
Glucocorticoids can be extracted from blood, faeces and saliva samples. Although blood samples are considered to be the most reliable source of glucocorticoids, obtaining them can be invasive and can act as a source of stress, skewing results. Ozella et al. (2017) used the non-invasive method of assessing faecal glucocorticoids to examine physiological stress caused to African Penguins in the presence of visitors, although they did not find an influence of this on faecal glucocorticoids.
Other types of measurements of stress in penguins
Other physiological measures of stress include body-condition scoring and evaluation of recurring health issues and poor recovery times, as well as monitoring of the internal environment. Culik et al. (1990) investigated the effect of disturbance on the heart rate and behaviour of nine incubating Adélie Penguins with the use of safety-pin electrode ECG and implantable radio-transmitters. Minimal resting heart rate was found to be 86 bpm (beats per minute) which rose to 127 bpm following disturbance by humans, and 145 bpm in the presence of a helicopter. Though the study sample was a wild group, the rise in heart rate, indicating stress, can be applied to captive groups. On the other hand, the study also found evidence of habituation to human presence in a hand-reared chick. This suggests that captive penguins can also experience habituation to human-related stress.
Welfare assessment on penguins requires wider publication. However, trial of behavioural and physiological measures will allow keepers of captive populations to discover the most appropriate methods for their group and individual penguins.
Animals can experience a lot of stress and react is various ways. It’s incredible. Please help us continue to bring you this type of information by donating to Penguins International.
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Culik B., Adelung D., & Woakes A.J. (1990). The Effect of Disturbance on the Heart Rate and Behaviour of Adélie Penguins (Pygoscelis adeliae) During the Breeding Season. In: Kerry K.R., Hempel G. (eds) Antarctic Ecosystems. Springer: Berlin, Heidelberg
Ozella, L., Anfossi, L., Di Nardo, F., & Pessani, D. (2017). Effect of weather conditions and presence of visitors on adrenocortical activity in captive African penguins (Spheniscus demersus). General and Comparative Endocrinology, 242, 49-58. https://doi.org/10.1016/j.ygcen.2015.12.002
Sherwen, S. L., Magrath, M. J. L., Butler, K. L., & Hemsworth, P. H. (2015). Little penguins, Eudyptula minor, show increased avoidance, aggression and vigilance in response to zoo visitors. Applied Animal Behaviour Science, 168, 71-76. https://doi.org/10.1016/j.applanim.2015.04.007