Maternal tactics for preventing predation of newborn fawns
The time immediately after birth, known as the postpartum period, is a very risky time for ungulate infants. They are small, weak, and unable to run and are thus easily killed by predators. Once a gazelle is born, the fawn and its mother enter a race against the clock to get the fawn hidden before a predator detects and kills the newborn. For this study, I observed eleven mother-fawn pairs during the postpartum period and noted the habitat (short or tall grass) and social context (in a group or alone) in which parturition occurred. I measured how long it took for the fawn to move away from the birth site and begin hiding or be killed by a predator, and recorded any disturbances to the mother-fawn pair by other non-predator animals.
In my study, 6 of the 11 fawns were encountered by predators within an hour of birth and all but one of these were killed. I found that there are two effective tactics mothers can use to improve their fawn’s probability of surviving the treacherous postpartum period: they can either leave their social group and give birth alone in a tall grass habitat OR they can remain in their social group and give birth in their normally-preferred short grass habitat. The first strategy reduces the duration of the postpartum period (that is, fawns are able to stand, walk, and ultimately hide sooner) because the mother-fawn pair suffers fewer disturbances. However, this strategy increases the detectability of the fawn because a lone female in tall grass is a pretty sure sign to predators that there is a fawn nearby. The second strategy reduces the detectability of the fawn (because the mother and fawn are less conspicuous when they are within a group of other gazelle), but increases the duration of the postpartum period (because other gazelle are attracted and displace the mother from the fawn, which means it takes longer for the fawn to develop the ability to stand). Fawns whose mothers use one of these two strategies had about a 60% chance of surviving until hiding. In comparison, the females that did not use one of these strategies (that is, they gave birth alone in short grass or in a group in tall grass) all lost their fawns within the first hour of life.
In this course of this study, I observed several instances of warthogs attacking and/or killing newborn gazelle (click here for a video), a behavior that had not been previously documented. The window of opportunity for warthog predation seems to be pretty limited: to kill the gazelle, the warthog first has to knock it over and hold it down with a hoof. Once they are an hour or two old, gazelles are able to recover from being knocked over fairly quickly, and thus avoid being killed. Warthogs were very numerous at Ol Pejeta while I was conducting this research, so the encounter rate between warthogs and gazelle neonates may have been unusually high, which might explain why I observed this behavior but previous researchers did not. Interestingly, tommy mothers do not exhibit antipredator behavior in response to warthogs near their young, providing further evidence that this is a rare or emerging predator behavior.
The video below shows a fawn’s postpartum period, starting approximately 20 minutes after birth, during which the fawn is learning to stand, walk and nurse. The fawn’s mother gave birth within a herd so the mother-fawn pair suffer some disturbances by conspecifics. However, this video has a happy ending as the fawn survives to begin hiding.
Roberts, B.A. and Rubenstein, D.I. 2014. Maternal strategies for mitigating neonate predation risk during the postpartum period in Thomson’s gazelle. Behaviour 151: 1229-1248. PDF
Roberts, B.A. 2014. The trials of motherhood: maternal behavior patterns and antipredator tactics in Thomson’s gazelle (Gazella thomsonii), a hiding ungulate. PhD thesis, Princeton University. PDF
Roberts, B.A. 2012. An attack by a warthog (Phacochoerus africanus) on a newborn Thomson’s gazelle (Gazella thomsonii). African Journal of Ecology 50: 507-508. PDF