Feeding behaviour of six bottlenose dolphin newborns in controlled environment

FEEDING BEHAVIOUR OF SIX BOTTLENOSE DOLPHIN NEWBORNS IN CONTROLLED ENVIRONMENT 1-2 Raffaella Tizzi, 2 Francesca Triossi, 1-3 Elisabetta Cancellieri and 3 Pier Attilio Accorsi 1Delfinario Rimini, Lungomare Tintori 2, 47921 Rimini, Italy. Email: raftizzi@tin.it 2Oceanomare-Delphis ONLUS, Via G. Marinuzzi 74, 00121 Roma, Italy. Email: danielasilvia.pace@gmail.com 3Dipartimento di Morfofisiologia Veterinaria e Produzioni Animali, Università degli Studi di Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia (BO), Italy. Email: pierattilio.accorsi@unibo.it In cetaceans, the social organization of many species, included bottlenose dolphin (Tursiops truncatus), presents at its basis the mother-offspring relationship, as mothers provide the bulk of parental care by virtue of the nursing relationship. The relatively problematic access to lactating females and their calves has complicated studies of suckling behaviour so that early developmental profiles of feeding are almost completely lacking. The birth of six healthy bottlenose dolphin calves, in different periods in two distinct facilities, provided an opportunity for studying mother-calf interactions. The aim of the present investigation was to analyze, week by week, the newborns' feeding behavior throughout their first year of life. As a consequent goal, the study intended to identify suckling trends useful for newborns' healthiness diagnosis. The subjects of the study were two newborn bottlenose dolphin males, Tabo (1993) and Golia (1993) housed in Aquatic World Delphinarium (Cattolica, RN, Italy) together with two newborn female, Luna (1995) and Blue (1997), and two newborn males, Rocco (2003) and Lapo (2007), housed in the Rimini Delfinario (Italy). While Tabo, Luna, Rocco and Lapo were given birth by expert females, Golia and Blue were calves of first time mothers. Both facilities consisted in open-air pools with underwater windows for visual observations below the surface. Suckling behavior was systematically monitored from birth to 52 weeks of age of calves for a total of 1745 hours of observation. The sampling method applied was the "Focal animal sampling", with continuous recording sessions lasting 30-120 minutes. Observer 5.0 (Noldus) was used to calculate frequency and duration of the following parameters: hourly frequency of both a) suckling attempts and b) successful suckling episodes and, c) mean suckling time per feed. The highest frequency of unsuccessful suckling episodes was observed in the first week after the birth (2.70 ± 1.24 events/h). In this crucial period, mother's calving experience seems to be crucial as well as the role of newborn in finding the correct position of the nipples and in learning the correct suckling behavior. A progressive, clear decrease of nursing attempts was observed during the following weeks, with newborns going to perform almost only effective suckles since the second semester of life. The average time of first real suckling - entailing the insertion of the rostral tips into either of the mammary slits and the ensuing intake of milk - was 7.48 ± 8.95 hours after the birth, with a low of 3.20 hours in Lapo and a high of 20 hours in Golia. Regarding the successful suckling trend, the results underlined a very slight decrease of mean frequencies with the calves' growth (tendency line of the mean: y = -0.0099x + 0.5907, R2= -0.1724). The nursing tended to shift from about 3 events per hour in the first weeks (maximum value 3.8 events/h in the first week of life), to about two suckling bouts per hour in the rest of the period. The mean suckling time per feed remained between 3 and 5 seconds, with a maximum duration of 5.3 seconds expressed in the first week after the birth. As for suckling time trend, no significant variations appeared with calves' age. At the same manner, no preferences in the use of either of the mother's mammary slits emerged. During the first month of life, the feeding appeared often associated to a 90...