Hypothermia is one of the major causes of mortality in neonatal piglets. Piglets must therefore rapidly adapt to post uterine life and achieve thermal homeostasis by starting thermogenesis and heat preservation. Rectal temperature 2 hours after birth is a strong indicator of their success. The aim of the study was to identify the causes of individual differences in successfully achieving thermal homeostasis. Behavioural and physiological data were collected on 635 liveborn piglets from 45 farrowings in either crates or pens. The data included: birth weight, hypoxia at birth (viability score and lactate in umbilical cord blood), latency to first udder contact and first suckle, scans of individual piglet position during the first 2 hours after birth, rectal temperature at birth and 2 hours post partum. A graphical chain model was used to analyse data. Bayesian-Information-Criteria (BIC) was used for model selection. BIC relates to maximum likelihood but introduces an additional penalty term for the number of parameters. Strength of the association between two variables is reported as an increase in BIC (BICinc) by removal of the link. Three variables had direct links to rectal temperature 2 hours after birth. There was a positive relation to birth weight (BICinc=25.7), and to being observed more often by the udder as opposed to alone during both the first (BICinc=7.6) and second hour (BICinc=18.7) after birth. Lighter piglets and piglets that had experienced hypoxia took longer to achieve first suckle, which in turn affected behavioural thermoregulation. In conclusion, high birth weights and staying close to the udder during the first two hours of life were critical for piglets' success in achieving thermal homeostasis. The birth process and hypoxia affected piglet behaviour during the first two hours after birth. The results of this study can help identify means of preventing hypothermia and decrease piglet mortality.