title: Behavior and body mass changes of a mother and calf Pacific walrus (Odobenus rosmarus divergens) during the suckling period.
abstract: The behavior of a 13-year-old female Pacific walrus and her first calf is described during the first 7 months of the 19-month suckling period. The calf vocalized before 62% of suckling sessions. The mother immediately responded after 84% of vocalizations; after 44% she allowed a suckling session. The number of suckling sessions per 24-h period decreased from on average nine in the second week after birth to two by the thirteenth week. Thereafter, the number of suckling sessions fluctuated between 3 and 5/day. The average suckling session duration increased from 4 min/day to around 17 min/day. The average effective suckling time per session increased from on average 2 to 10 min. The number of breaks decreased during the study period from around 40 to 20 per session. The mother spent on average 47% of her time resting, the calf 44%. The remaining time was spent in locomotion, and suckling, playing, investigating, and looking. Mother and calf spent on average 51% of time indoors. The mother spent 43% of her time in the water, the calf 39%. The calf's body mass at birth was 55 kg; it increased to 178 kg at 27 weeks. The mother did not eat for the first 5 days after delivery, and she ate less than usual during the next 6 days. The mother's mass eventually stabilized at 1024 kg (>before gestation). The calf was not given formula and was weaned onto fish. This is the first detailed description of a captive Pacific walrus's suckling period. It could benefit the husbandry of future captive-born walruses, and may elucidate the behavior of wild walruses during suckling.
authors.affiliation: Sea Mammal Research Company (SEAMARCO), Julianalaan, Harderwijk, The Netherlands.
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Kastelein
authors.forename: Ivanka
authors.initials: I
authors.lastname: van den Belt
authors.forename: Nancy
authors.initials: N
authors.lastname: Jennings
authors.forename: Richard
authors.initials: R
authors.lastname: de Kruijf
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D000833:Animals, Suckling / Q000502:physiology*; D000836:Animals, Zoo; D001835:Body Weight / Q000502:physiology*; D004032:Diet; D005260:Female; D008425:Maternal Behavior / Q000502:physiology*; D019370:Observation; D014828:Vocalization, Animal / Q000502:physiology; D014856:Walruses / Q000502:physiology*
keywords: behavior; composition; growth; milk; pinniped; reproduction