An enclosure renovation has an obvious purpose: give animals a better place to live. Getting there can involve demolition, unfamiliar activity and temporary restrictions on where the animals can go. How can keepers tell what the transition costs each resident?
Neeti Jain, Rachel M. Santymire and Jason D. Wark had an unusual opportunity at Lincoln Park Zoo. They followed two female giraffes across a long construction project and continued monitoring after a larger outdoor enclosure became available. Their record eventually included another major change: the older giraffe became seriously ill and died, leaving her longstanding companion behind.
The resulting paper is valuable because its measures did not all tell the same story. Two animals sharing an environment responded differently. For the surviving giraffe, even two laboratory measures taken from dung changed in opposite directions after her companion's death. Those differences help explain why a welfare assessment cannot simply label an animal stressed or unstressed from one number.
Following individuals through a changing enclosure
The females had lived together since 2003. At the end of the study the older animal was 28 and the younger 18. Monitoring extended from October 2014 to October 2017, through demolition, a pause in work, active construction, completion of the project and eventual access to the expanded outdoor area.
Researchers collected faecal samples two or three times a week. These contain breakdown products of glucocorticoids, hormones involved in the body's responses to challenge. Measuring those metabolites can reveal changes in adrenal activity without drawing blood or restraining the animal. It does not directly measure a feeling, identify its cause or tell whether every rise is harmful.
Alongside the laboratory work, observers recorded behaviour during ten-minute sessions, noting the animal's activity each minute. Their categories included feeding and rumination, inactivity, movement and repetitive behaviours such as pacing or licking objects. Across the study they collected 681 sessions. Behavioural sampling began later than hormone sampling, so the construction comparison of behaviour did not include the demolition period.
This was an extended observation of events the zoo was already undertaking. There was no untouched comparison herd and no complete period before demolition against which to measure everything that followed. The researchers instead compared successive phases and each animal's own measurements. That design can reveal changes aligned with events, while leaving several possible causes entangled.
Shared disturbance, different responses
Faecal cortisol metabolite levels were high for both giraffes during demolition. During the later active construction phase, however, the older female still had relatively high concentrations while the younger female had her lowest phase average.
The behaviour records also distinguished them. The older giraffe moved more and performed more repetitive behaviours during active construction, while spending less time inactive. The younger animal did not show the same broad pattern. Figure 7 makes the contrast visible: the conspicuous changes in the older female's activity categories are largely absent from the younger one's panel.
The result cannot establish whether age, personality, previous experience or another individual difference explained the contrast. There was one animal of each age and type, so those possibilities cannot be separated. Nor can the study isolate building noise from changes in access to outdoor space; construction brought several changes together, and sound levels were not measured.
Access to the completed, larger outdoor enclosure did not produce a clear change in cortisol metabolites for either female relative to the preceding phase. That is a result about one measure during this sequence. It does not establish that the additional space had no value.
A separate study by Miho Saito and colleagues provides a useful comparison. When two adult females were observed indoors in one year and outdoors at night in another, one had longer lying bouts outdoors while the other had shorter bouts. Those conditions also differed in more than location. Both studies make individual responses visible; neither supports a simple rule that a housing change must move every animal's measurements in the same direction.
When a companion became ill
The older female's final months brought repeated illness. Her cortisol metabolite concentrations increased, but the researchers did not detect a corresponding clear change in her overall activity categories. A giraffe could therefore look broadly similar in these observations while another part of the record changed substantially.
After her death, her companion's faecal cortisol metabolites increased. Yet corticosterone metabolites, measured from the same type of samples as another candidate indicator, decreased. The paired bars in Figure 3 show the disagreement particularly clearly. Choosing one marker or the other would have changed the apparent direction of the response.
Plains zebras were also introduced to share the survivor's outdoor enclosure during July and August 2017, so the later observations did not isolate the effect of losing a giraffe companion.
The authors considered cortisol the more informative measure for these events. They also discussed possible changes in the stress-response system, but the study did not diagnose that mechanism. Laboratory validation of an assay and an association with a consequential event are different from proving the internal process that produced the pattern.
The survivor did not develop the predicted increase in repetitive behaviour after losing her companion. Such behaviour had already fallen during the older female's illness and remained lower afterward; ordinary movement also declined after the death. These observations do not let researchers name an emotion such as grief, or conclude that the absence of increased pacing meant the loss was unimportant.
The practical lesson comes from the disagreement itself. An animal's behaviour, health history, social circumstances and physiological measurements can each expose something the others miss. Following the same giraffe over time makes those discrepancies visible—and turns an apparently reassuring or alarming single observation into a question that can be investigated.
Sources
- 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. Full paper.
- Saito, Miho; Matsunaga, Masayuki; Fukuizumi, Hiroki; and Nakamichi, Masayuki (2024). “Effects of nocturnal outdoor enclosure access on space use and sleep-related behaviour in captive giraffes.” Journal of Zoo and Aquarium Research, 12(3), 154–163. Related study.
