Most ungulates are surprisingly inept at using their horns against predators, part 2: is the sable antelope (Hippotragus niger) really an exception?

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...continued from https://www.inaturalist.org/journal/milewski/52018-most-ungulates-are-surprisingly-inept-at-using-their-horns-against-predators-part-1#

The sable antelope (Hippotragus niger, https://www.inaturalist.org/taxa/42334-Hippotragus-niger) may be an 'exception that proves the rule'.

It is true that the sable antelope is more formidable than most other ruminants in defending itself from carnivores. This is evident in video footage (https://www.facebook.com/100070824108397/videos/sable-antelope-fights-with-lions-to-regain-their-lives-fiercely-/1119903748631124/ and https://www.youtube.com/watch?v=MPLMaYBBoyY and https://www.facebook.com/cnnnews18/videos/antelope-uses-curved-horn-to-escape-lions-attack/2179038852266226/ and https://www.facebook.com/100054095415612/videos/sable-antelope-fighting-back-against-lion-but-baboons-were-alerting-the-sable-un/901875494180681/).

Please note that

• slow-motion shows that, in the struggle depicted, the victim moved its head sharply backwards, striking the back of the lion with its horn-tips (albeit apparently not forcefully enough to puncture the skin of the carnivore), and
• the fact that the attacker fled into and across the water, rather than running on dry ground, suggests that it feared charging retaliation by the victim.

However, it is also true that the sable antelope exhibits remarkably poor parental protection against predators.

What this means is that, in the broader anti-predator context,

• any advantage to survivorship in adulthhood (by means of violent self-defence) is potentially cancelled by disadvantage to survivorship in youth (owing to parental 'negligence'), and
• the adaptive value of aggressive demeanour, combined with horns designed to stab, is ultimately social rather than anti-predatory (https://d1wqtxts1xzle7.cloudfront.net/38898576/Franklin_Vicuna_1974.pdf?1443280555=&response-content-disposition=inline%3B+filename%3DThe_Social_Behavior_of_the_Vicuna_p_477.pdf&Expires=1698197616&Signature=C5l0th2BZxpIcpy9deqhWgYrQ10WrdtIry8oRr-oqS9Plx4GR1d-D5sw1dOtLDtddHFsjeP0WWGehyFgKsGijbR~H0AG5DEA-8TusHqchFfDwAVTJ5~9OW3T0kHJ3uP0wrpyXurbUYgHDjrKbBrj9ONjuszUKpeWy374tpDNboSDP4BDxakA-qJ9QqO5lSoIeeMHyHOjN~wKScz~dyGZLnY0Btp-GUtHrSCZH~Vnfu5ypOqkBj0t64Mjc8vL5BVB6~EqbFCGklRKCmIRsXoCAaLOtbAOyKemOyHnnXZS6Q6fccQxYnI-E13pobA~jOExMNYmVwmONpVZmofuHlyMZQ__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA#page=164 and https://onlinelibrary.wiley.com/doi/abs/10.1002/zoo.1430120205).

On the topic of the sable antelope, https://www.youtube.com/watch?v=Le7MPaVDDhU contains some relevant points, particularly a defensive formation of gregariousness surrounding infants. However, what this commentator does not mention is that infants/juveniles tend to lag behind the group during locomotion, exposing themselves to predation (Estes 1991).

(Incidentally, please note that, in this population in Texas, many adults seem to have somewhat deformed horns.)

How effective, in reality, are horns of the sable antelope against predators?

On one hand, "The long horns with their sharp points are deadly weapons and quick sweeps have caused serious injuries to hunters who have dared to approach too close to wounded sable" (Skinner and Chimimba, 2005, page 664).

On the other hand, "sable antelope are highly susceptible to predators and lions seem primarily to blame for driving the decline in the species at [Malilangwe Game Reserve]" (Capon, 2011, https://www.semanticscholar.org/paper/The-ecology-and-potential-factors-limiting-the-of-%3A-Capon/44114575d1aeacf0003baed22d223bb8eea164e4).

Estes (1991, page 119) states: "Though horse antelopes are considered by hunters to be among the most dangerous antelopes, and even lions are sometimes fatally stabbed, their dangerous horns and stabbing technique do not deter predators from hunting them and are probably rarely effectively employed (Eloff 1964)...The habitats frequented by these antelopes usually have relatively few predators, perhaps permitting a certain slackness in their antipredator behaviour". (By 'horse antelopes', Estes means hippotragin bovids, https://www.inaturalist.org/observations?place_id=any&taxon_id=846296&view=species.)

It is worth quoting in detail from Estes (the pre-eminent authority on the sable antelope), to show just how 'negligent' the sable antelope can be, parentally.

My source is an unpublished report, viz. Estes R D and Estes R K (1969, page 15), 'The Shimba Hills sable population', First Progress Report of Hippotragine Antelope Study to National Geographic Society, August 1969.

"the bond between mother and calf is comparatively loose. Not only do calves seldom move beside their mothers, but cows sometimes absent themselves from the herd and their calves for hours or even days. Thus it happened several times that when the...herd divided, a few young calves ended up separated from their mothers. Eventually the calves, presumably motivated by hunger, began to seek them and to utter distress calls with increasing frequency and volume, that we at first mistook for the alarm cries of a bird. When their mothers failed to return, the calves began wandering from the herd, calling, listening, then coming back. One finally left the herd altogether and was not seen with either herd for several days. Meanwhile its mother was several miles away and was never seen to make the slightest effort to locate her offspring. Even the playing of a tape recording of her calf's distress call elicited only brief interest - less than was shown by other nearby calves. Surprisingly enough, the calf was reunited with its mother by the following week, apparently none the worse for the ordeal. As this particular female was an exceptionally poor mother, the example is not typical. Wide differences in the degree of attentiveness to the young were evident. There were several cows, for instance, that regularly accompanied the calves, forming a recognisable nursery sub-group. Nonetheless, it is the rule in sable that calves accompany their mothers only during and immediately after feeding. Almost invariably, the mother moves off before her calf has suckled its fill, and it then follows closely behind her for several minutes in an unsuccessful attempt to resume suckling. Assuming that newborn calves are concealed for the first few weeks of life, as is the case in the related roan and oryx, minimum contact between mother and offspring may be seen as the pattern from the very outset."

Skinner and Chimimba (2005, pages 665-666) state: "the calf...conceals itself in a sheltered place in woodland, in patches of grass, or in underbrush...Grobler (1980..., https://journals.co.za/doi/pdf/10.10520/AJA03794369_3018) mentions that up to 11 calves have been found hiding together."

My commentary:

I take the above as indirect evidence that it would be unlikely for any juvenile of the sable antelope, attacked by predators, to be defended by adults.

This is significant because the horns of females, even more than those of males, seem designed to be effective anti-predator weapons. They retain sharp points, and they are straight enough to be used to stab forward, yet curved enough to reach an attacker located behind the head (https://howieswildlifeimages.files.wordpress.com/2017/03/20151014-d4s_4612-2.jpg).

I suggest that the sable antelope is an 'exception that proves the rule', in the sense that its self-defence by means of its horns confers no net anti-predator advantage. The horns may have evolved less in response to selective pressures of predation than in response to the particular social strategy of the species, in which agonistic interactions among females, and self-defence by females against males (http://swartrivierwildlife.co.za/blog/2016/9/11/game-animal-dominance), ensures an appropriate sharing of resources, in the presence of gregariousness but the absence of sexual segregation in space.

ADDITIONAL NOTES, with particular reference to

• CAUDAL FLAGS and
• the African hunting dog (Lycaon pictus):

The following (https://www.youtube.com/watch?v=WAPh8Bch5xU) is valuable in showing details of an interaction between the sable antelope and Lycaon pictus.

My commentary is as follows:

Firstly, this footage shows a behaviour that may not have previously been recorded. This is the rapid and continual horizontal wagging of the tail by Hippotragus niger in a stand-off with Lycaon pictus.

The use of the tail as a caudal flag in Hippotragus is poorly documented in the literature. What is significant in this case is that the horizontal wagging of the tail differs from the erection of the tail seen in various other ungulates when alarmed. The horizontal movement means that the caudal flagging may perhaps produce a 'strobing' effect against the white patch on the buttocks, if viewed from behind.

Also note another behaviour possibly never recorded before: as the individual of H. niger lowers its horns in an almost choreographed way, it simultaneously utters a loud, protracted snort - different from the normal snort of alarm, and perhaps having a vocal component.

So, the defensive display consists of

• the dynamic component of the lowering of the horns,
• the dark-pale contrast presented by the face, which is a kind of 'frontal flag' in terms of adaptive colouration, and
• the audial accompaniment of the specialised snort.

(Another bovid with a combination of snort and vocalisation, 'warning off' intruders, is Connochaetes gnou, https://www.facebook.com/watch/?v=870370330095038.)

It seems significant that, although H. niger does lower its horns defensively, the main form of counter-intimidation is the flailing of the fore hooves while feinting forward (similar to giraffes in similar situations).

Even a hippotragin bovid, belonging to a clade somewhat renowned for the anti-predator use of the horns, seems instead to advertise its capacity to kick forwards, in this emphatic way. The implication is that the risk posed by the horns has been overstated in the literature.

Some questions:

• If this adult male individual of H. niger, when harassed by a group of L. pictus, ran down to a pool of shallow water, was this because it sought the option of retreating even further, into deeper water, were the carnivore to persist with the attack?
• Did it seek partly to use Hippopotamus amphibius - which tends to be irascible in an unintelligent way - as a form of distraction (collateral defensiveness)?
• Was the idea merely to find a situation as much out in the open as possible (as opposed to backing into a patch of thorny cover to protect the hindquarters, and then fighting with the horns)?
• Was this individual somewhat 'torn' between an attraction to water as a refuge, and fear of Crocodylus niloticus?

On the topic of caudal flags, please note the various gradations of caudal flagging in L. pictus, ranging from

• inert tail while standing attentively but stationary, or while stalking with head lowered, through
• erratic flicking of the lowered tail to one side when walking/trotting indecisively, to
• raising the tail above the horizontal when either breaking into a run (however brief the acceleration), or approaching the prospective prey dangerously closely.

Lycaon pictus is a prime example of a carnivore possessing a caudal flag (https://www.dreamstime.com/african-wild-dog-lycaon-pictus-namibia-image198639762 and https://www.dreamstime.com/african-wild-dog-lycaon-pictus-pack-kill-greater-kudu-female-carcass-namibia-image196305261).

The footage reveals low-intensity aspects of this, and suggests that the various positions of the tail are complex enough to form a rudimentary 'sign language' in L. pictus. The wolf (Canis lupus) does not show similar caudal flagging, and the dhole (Cuon alpinus) needs further investigation.

Also note that the individual of H. amphibius (which is adult male, based on the proportional size of the head) has an inert tail as it stands still, watching the drama unfold.

Posted on October 24, 2023 04:51 AM by milewski