Top marks from top dogs: tandem marking and pair bond advertisement in African wild dogs

1. What they did

In many pair-bonded canids and antelopes, both members of a pair scent-mark the same spot, one on top of the other. This is called tandem marking. It is usually thought to help a pair bond form, or to advertise to others that a mated pair holds the territory. The authors wanted to know who marks first and who ends up “on top”, because the top mark at a site seems to matter most to the animals that visit it later.

They watched the dominant pairs of 13 free-ranging African wild dog packs in northern Botswana between May 2011 and September 2012. Almost all the dogs (95.5% of 112) were of known age and origin, and each was recognized by their unique coat pattern, ear notches and tail stripes. One to four dogs per pack wore radio collars so the packs could be found from the air and from a vehicle.

From a vehicle, the observers recorded on video or datasheets every urine mark the dominant pair made with a leg posture (cocked leg, raised leg or handstand), every time a dog sniffed or licked a mark, and every overmark, until the pack left the site. Squat urinations and defecations were left out, as earlier work suggests they are not signals.

Two of the 13 dominant pairs were full siblings: after a dominant died, a brother or sister of the survivor took over the role. These “related” pairs have no breeding opportunity inside the pack, so the authors compared them with the 11 “unrelated” pairs.

2. What they found

Who marks and who ends on top

• The dominant pairs marked at 502 sites. The dominant male started marking at 69.32% of sites and left the top mark at 80.29%.
• Marks started by females were much more likely to be tandem-marked (85.06% of 154) than marks started by males (40.23% of 348).
• Males always tandem-marked female marks that they sniffed. Females sometimes sniffed or passed close to a male’s mark and walked away without marking, which suggests an active choice.
• Both sexes were more likely to overmark a site where their partner’s scent was on top than one where their own scent was already on top. Marks that were already layered (double or triple marks) were sniffed and overmarked at similar rates to single marks, which shows that the top scent is what counts.

Related versus unrelated pairs

• Marks were more likely to become tandem marks in related pairs (75.29% of 85 sites) than in unrelated pairs (60.05% of 418 sites).
• Males were on top at the end of marking more often in unrelated pairs (82.73% of sites) than in related pairs (68.24%).
• In related pairs, females left a much larger share of the marks that were never tandem-marked (42.86% of 21, against 14.53% of 172 in unrelated pairs). Males did not pass close to the female marks they missed, so these females seem to have placed marks where the males would not find them.
• Marking bouts were about twice as long in related pairs (an average of 4.20 marks per bout) as in unrelated pairs (2.41 marks per bout).

Through the year

• Every month, a higher proportion of female-started marks than male-started marks were tandem-marked.
• In June and July, when the dominant female stayed near the den, almost all of her marks were tandem-marked, and almost none of the male’s were.
• Males tended to tandem-mark more during the female’s short receptive period in April.

3. What they concluded

• Dominant African wild dogs pay attention to which scent is on top of a marking site and are motivated to put their own scent in that top position.
• Males were more likely to cover their partner’s marks than the other way round, which fits the idea that advertising the pair bond, and guarding a mate, matters more to males. The authors link this to males being more at risk: male wild dogs disperse farther, so resident packs may meet roaming males more often than roaming females.
• In unrelated pairs, females may use a “test and assess” strategy: by marking a lot, they show whether their male can keep covering their scent, and the pattern advertises both a working pair bond and a high-quality male who is not available.
• In related pairs, where a working pair bond would not help, females seem to advertise themselves, perhaps to attract an unrelated male from outside the pack. They kept more of their marks apart from the male’s, and marking bouts were longer, perhaps from competitive overmarking within the pair.
• It is unclear why related males keep marking as if advertising a pair bond. Experiments presenting single and tandem marks to potential immigrants are needed.
• The results rest on only two related pairs, so more work is needed to test these ideas.

6. Other technologies, skills or innovations

• Radio collars (Vectronic and Sirtrack), located by radio tracking from the air and from a vehicle. Dogs were darted from a vehicle and immobilized to fit the collars; the authors report no negative effects observed.
• Individual identification from drawings and photographs of each dog’s coat pattern, ear notches and tail stripes.
• Video and datasheet recording by critical incident sampling (recording every marking event as it happens).