Behavioural responses of ex-situ captive hippopotamus (Hippopotamus amphibius) in lactation season: Maternal investment and plasticity of infant self-independence
Behavioural responses of ex-situ captive hippopotamus (Hippopotamus amphibius) in lactation season: Maternal investment and plasticity of infant self-independence
1. Department of Evolutionary Ecology and Genetics, Zoological Institute, University of Kiel, Kiel 24118, Germany; 2. Ecology Center, University of Kiel, Kiel 24118, Germany; 3. Hangzhou Wildlife Park, Hangzhou 311422, China; 4. Breeding Base for State Key Laboratory of Subtropical Forest Cultivation, Zhejiang A & F University, Zhejiang University, Hangzhou 311300, China
In order to promote hippopotamus management in the captive and ex-situ environment, especially the control of behavioural and physiological status during breeding and lactation seasons, we conducted a preliminary study on behavioural responses of a pair of hippos including both mother and infant in Hangzhou Wildlife Park, China. The study of the captive hippos for about 1-month in the lactation season was carried out during August and September, 2009. The behavioural patterns were identified by all occurrence sampling and instantaneous scanning sampling methods with 5–10 min intervals. As a result, mother-offspring conflicts and interactions did occur throughout the whole study period. Early maternal investment showed a positive trend in activity rhythms (slope= 0.0014, Z = 0.3027, P<0.001) and a negative trend (slope= -0.0066, Z = 0.8807, P<0.001) in territorial occupation of water, all of which supported our hypotheses that the mother hippo might exert less care for the infant and cut down on her own obligations in nursing. For infant self-independence, during the whole lactation season, the primary trends of activities and territorial occupation dynamics of the infant hippo were slightly different from before, judging from linear models (slope= -0.0017, Z = 0. 3309, P<0.001). However, the frequencies of activities were not stable, especially at around 12 days of age. The trends of territorial occupation (slope= -0.0071, Z = 0. 904, P<0.001) also showed negative dynamics in water body occupation by the time the infant hippo grew up. The general trend (slope= -0.005, Z = 0.06, P<0.001) of suckling dynamics was demonstrably negative, with an upwards fluctuation at period 3 (10–15th day). This also illustrated that as the infant developed, the dependency on the mother was reduced at the end of the lactation season. In addition, a sharp decline between P3 and P4 also supported the mother-offspring conflict theory. In general, time budgets of hippos in active behaviour were (31.8±2.1)% for the mother and (32.1±2.6)% for the infant. Spatial distributions in water within temporal limitations were (80.1±2.7)% for the mother and (81.8±2.7)% for the infant. Behavioural dynamics showed strong synchronous relations between maternal investment and infant independence. Our current short-term investigation proves to be a key in management and conservation of hippopotami during the lactation season.
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