Response of Female White-Tailed Deer to Scrapes and Antler Rubs

1. What they did

Male white-tailed deer make scrapes (pawed patches of ground) and antler rubs (trees with the bark frayed off) during the breeding season. These signposts were thought to help males show dominance, but little was known about what they tell females. The authors reported an earlier study of how females react to them.

They followed three tame female deer that roamed freely on a 337-hectare (ha) university forest in Georgia, United States, between May 1979 and February 1980. The females’ food habits, movements and home ranges appeared typical of wild deer in the area, and all three were bred by wild males during the study. Observers carried out 45 observation periods of 24 hours, each made up of two 12-hour sessions, usually watching from only 2 to 5 m away. They recorded every time a female came within 20 m of a rub or a scrape, and what she did.

2. What they found

Antler rubs

• There were 100 incidents in which a female was within 20 m of a rub (September 1979 to February 1980).
• Between 6 October and 14 January, the females responded to rubs in two ways. First, a female would pause for several seconds, sniff the bare wood, and usually lick or nibble the rub and the frayed bark around it. All three females did this, but the dominant female accounted for nearly half of these observations. Sniffing, licking or nibbling happened in 23 of the 100 incidents (23%). The rate of response stayed about the same through the season.
• Second, only the dominant female rubbed her forehead on a rub, on four occasions (given as 5%). This rubbing was gentle, did not visibly change the rub, and always went together with sniffing, licking or nibbling.
• The three deer often travelled together, but when two or three were at a rub, only one responded. The 100 individual incidents were really 61 encounters by a lone deer or a group, and 23 of these (38%) involved a response. Which female responded did not seem to depend on dominance.
• Fresh rubs drew far more interest: 17 of 29 group encounters (59%) with rubs thought to be under 2 days old drew a response, compared with only 1 of 24 encounters with older rubs.

Scrapes

• There were 24 incidents in which a female was within 20 m of a scrape (27 October to 7 December 1979). The females seemed to come across scrapes by chance.
• Three behaviours were recorded: urinating within 20 m of the scrape, walking through the pawed patch, and sniffing it. Two females showed all three; the third showed none.
• At least one of these happened in 9 of the 24 encounters (38%): walking through or sniffing six times, and urinating nearby three times. Sniffing happened only at fresh scrapes, and the authors regard it as a clear response; walking through or urinating could have happened by chance.
• No female was seen smelling or licking the overhanging branch above a scrape, as another study had reported.

Breeding excursions

None of the females were under direct observation when they were likely mated. However, telemetry (tracking by remote location signals) showed that all three made an unusual trip outside their normal range around the time they conceived. These trips went 1.6 to 2.3 km from the centre of their core area and lasted about 24 hours.

3. What they concluded

• Scrapes and antler rubs probably carry breeding information between the sexes, as well as signalling dominance among males. Females may be able to tell a male’s dominance or physiological state from them, although what they actually learn is unknown.
• The females’ unusual trips at the time of conception were probably breeding excursions, to find suitable mates or their signposts.
• In other hoofed animals, such as sheep and goats, the smell of a male can bring females into breeding condition. Because male and female white-tailed deer may not spend enough time together for this, signposts could do the same job. The females’ responses support the idea that scrapes and rubs are a source of priming pheromones (scent signals that change the body’s state) that help bring on and synchronize the females’ breeding cycles.

6. Other technologies, skills or innovations

• Tame, free-ranging deer that could be watched closely (2 to 5 m) day and night.
• Focal-animal sampling with all-occurrences and instantaneous sampling.
• Telemetry to follow the females’ movements.