Winter housing changes more than the view from a giraffe's enclosure. Outdoor space, footing, browse and feeding opportunities may all differ when a zoo protects its animals from cold weather. A comparison between summer and winter therefore asks about a package of daily conditions, not simply a roof.
Catherine B. Razal, Jocelyn Bryant and Lance J. Miller followed four reticulated giraffes at Brookfield Zoo to see how that package related to behaviour, lying down and adrenal activity. They compared a month in summer 2015 with a month in winter 2016.
The measurements did not converge on a simple verdict. Some individual behaviours changed, while resting and hormone comparisons did not show clear seasonal differences. The study's useful contribution is to show what such a mixed result looks like before it is compressed into a claim that indoor housing either harmed the herd or made no difference.
Four animals and three ways of watching
The group comprised three adult females, aged eight, ten and twenty-five, and the ten-year-old's two-year-old male calf. In summer they had round-the-clock access to a large outdoor enclosure with dirt, grass and surrounding vegetation. Winter access was limited to a much smaller indoor enclosure and holding stalls, with concrete supplemented by rubber mats and wood chips.
Feeding also changed with the season. Summer browse carried leaves; winter branches did not. Hay remained available, and indoor management included feeding devices and opportunities to manipulate objects with the tongue. These differences could influence activity independently of floor area.
The team collected direct observations during the daytime, following each giraffe for fifteen-minute sessions across a randomized morning-and-afternoon schedule. Each animal contributed forty hours over the two study periods. Behaviour was recorded at regular instants, with some events counted whenever they occurred.
A second method extended observation through the night. Trained giraffes accepted ankle bands carrying acceleration loggers, which recorded leg position once a minute. Each animal wore a logger for eight separate twenty-four-hour periods across the study. The resulting records distinguished lying from being on the feet; they did not establish whether the animal was asleep.
Finally, keepers collected faecal samples for hormone analysis. Glucocorticoid metabolites in dung provide an indirect record of adrenal activity. The researchers checked the assay's laboratory behaviour, but could not perform a physiological challenge to validate its response in these giraffes. That matters when interpreting the measurement as an indicator of an animal's response to its surroundings.
An activity label needs unpacking
For analysis, the researchers combined feeding and rumination into one broad category. Another category combined movement, standing, exploration and several other nonfeeding behaviours. These groupings helped analyse a small dataset, but their everyday names can mislead unless their contents are explained.
The ten-year-old female spent more time in the feeding-and-rumination category during winter. The underlying figures show that the increase came from feeding: its observed share rose from 39% in summer to 64% in winter, while rumination was slightly lower. The combined increase therefore does not mean that both parts increased.
The oldest female and the young male showed more nonfeeding activity during summer. Standing alert accounted for much of their difference, alongside greater observed locomotion. Calling them simply “more active” would invite the reader to imagine that the whole change represented additional walking.
Figure 2 presents all four animals separately, allowing those different patterns to appear. At the group level, the researchers did not find clear seasonal differences in the combined behavioural categories. They also found no clear changes in measured behavioural diversity or abnormal repetitive behaviour. A herd-level comparison could thus miss changes that mattered to particular animals.
The authors proposed several possible explanations. Outdoor stimuli could encourage alert standing, while indoor feeding arrangements and leafless branches could occupy an animal for longer. The study did not manipulate those features separately, so these remain hypotheses about the observed responses.
A higher average is not a resolved hormone result
The posture records showed no clear seasonal change in lying time for the individuals or group. There was a positive relationship between the hourly patterns in summer and winter, consistent with some similarity in when the animals lay down. Similar timing does not establish identical comfort, nor does a lack of a statistically clear change prove that the flooring was irrelevant.
The hormone results require the same care. The group's average metabolite concentration was higher in winter—about 4,262 compared with 2,307 nanograms per gram of wet faeces—but none of the individual seasonal comparisons was statistically clear. Figure 4 shows the higher winter bars alongside substantial variation.
That combination supports neither a demonstrated winter stress increase nor proof that winter housing caused no physiological change. Four animals observed during one month per season provide limited power to distinguish persistent differences from variability. Season, housing, feeding and other circumstances also moved together.
A later study by Neeti Jain and colleagues followed two giraffes through construction and a companion's illness and death. It found that cortisol and corticosterone metabolite measures could even move in opposite directions after the social loss. Those were different animals, events and assays, so the numbers cannot be compared as one scale. The connection is interpretive: a hormone measurement gains meaning from the event, the animal's history and the other evidence collected with it.
For winter management, the useful next step is consequently specific. Repeating observations across more months and years, and testing changes in feeding placement or opportunities to move, could show which features influence each giraffe. This study begins that inquiry by keeping the animals and measures separate enough to see where their stories diverge.
Sources
- Razal, Catherine B.; Bryant, Jocelyn; and Miller, Lance J. (2017). “Monitoring the behavioral and adrenal activity of giraffe (Giraffa camelopardalis) to assess welfare during seasonal housing changes.” Animal Behavior and Cognition, 4(2), 154–168. Complete illustrated paper. DOI.
- Jain, Neeti; Santymire, Rachel M.; and Wark, Jason D. (2021). “Evaluating physiological and behavioural responses to social changes and construction in two zoo-housed female giraffes.” Journal of Zoo and Aquarium Research, 9(4), 228–238. Related longitudinal study.
