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Crab-eating Fox - Cerdocyon thous
Stronger together: observation on crab-eating foxes (Cerdocyon thous) cooperatively oreying their potential predator.

We describe the first record of cooperative predation by two crab-eating foxes (Cerdocyon thous) 
upon an adult short-tailed boa (Boa constrictor amarali) at a Brazilian Cerrado spot. Although it is known that  C. thous forages in pairs or in small family groups, there has been no report of crab-eating foxes preying cooperatively on medium and large-sized preys until now. Our observation sheds light on a poorly-known aspect of  feeding behavior of C. thous that could not be recorded through scat analysis, which is currently main source of information on carnivores’ feeding ecology.

Our opportunistic observation of a pair of crab-eating foxes attacking and killing an adult short-tailed boa was made on September 2006. The interaction lasted about 20 minutes and happened at the end of the 
afternoon (ca.18:30 h), at an anthropized remnant of Cerrado, near MS-178 highway (20°58′ 10.85″ S /56°31′05.78″W), at the municipality of Bonito, Mato Grosso do Sul State, Brazil. The observation was filmed and photographed from a distance that did not influence the behavior of the animals. When first sighted, crab-eating foxes were already attacking the boa. Therefore, we do not know details on how the interaction started. However, it was possible to observe that the short-tailed boa was alive and actively trying to defend itself, curling up and striking 
back against the crab-eating foxes. No signs of 
crab-eating foxes’ den or litter were detected within 100 m of the site of interaction spot. No clues of defensive (parental) behavior (e.g., threaten and alert or siren calls) of the types reported for crab-eating foxes (Brady 1979, 1981; Lemos & Azevedo unpublished data) and other South American canids (Chatellenaz et al. 2018) were detected. This apparent lack of parental behavior reinforces the notion that 
this was a predatory, not defensive behavior.
During the whole observation crab-eating foxes acted jointly and cooperatively. Attacks consisted of alternate or simultaneous bites by 
the two crab-eating foxes to the short-tailed 
boa, followed by several jolts and strong pulls 
in opposite directions. The short-tailed boa 
constantly wrapped itself in order to protect its head, suggesting a defensive behavior. Joint 
attacks prevented an efective defense response 
by the boa, making it vulnerable against its 
attackers. After several bites, the boa started 
to show evident apathy and the crab-eating 
foxes signs of tiredness. Then the crab-eating 
foxes took turns on the attacking, while the 
other rested at the side. A lethal neck-bite 
killed the snake, which remained stretched, 
belly up, motionless on the ground. With the 
natural daylight gone, it was not possible to 
carry observations on the total ingestion of
the prey. However, after the death of the boa, 
the female crab-eating fox started growling at 
the male when the latter approached the snake, 
displaying a behavior that may indicate a sign 
of dominance and a sort of hierarchy during 
prey consumption.
Although C. thous is frequently observed 
foraging in pairs but not sharing resources 
most of the time (Brady 1979; Lemos & Facure 
2011), the two crab-eating foxes displayed 
elaborated sociality and an ability to kill a prey 
cooperatively. Similar cooperative behavior for 
subjugating larger prey has been reported for 
bush dogs, Speothos venaticus (Lund, 1842), 
a highly social canid that may live and hunt 
in groups of up to 12 individuals (Beisiegel 
& Ades 2002; Lima et al. 2012). Apparently, 
the uninterrupted attack to the boa, through 
several and alternating bites by both members of the pair, was an important strategy to 
successfully subjugate the snake, preventing 
effective defense.
Records of cooperative hunting on large preys 
for C. thous are virtually nonexistent to our 
knowledge, except for one single description 
by R. Rudran at Brady (1979), who reports an 
ambush of a tegu (Tupinambis sp.) by a pair of 
crab-eating foxes. At the occasion the canids 
displayed similar behaviors of alternating at repeatedly attacking the prey, followed by pulling 
it in opposite directions and, finally, growling to 
each other once the prey was killed. Our new 
record, combined with those of Brady (1979) 
and Chatellenaz & Guzmán (2015), suggests 
that the benefits of sharing food may occasionally drive species away from the general rule 
predicted for small canids (Moehlman 1989). 
Additionally, the observation indicates that crab-eating foxes may actually prey on snakes 
(Gonzalez et al. 2016), instead of only ingesting them through scavenging (Rocha et al. 
2004). Boas are not only a large prey but also 
a potential crab-eating fox predator (Almiron 
et al. 2011). Therefore, our record opens the 
possibility that pairs of crab-eating foxes may 
consume other large preys, including some 
found in scats that are generally considered 
as carcass intake.
Considering the lack of observational records 
on feeding behavior for South American canids, 
our report is an important contribution for the 
current knowledge on the feeding ecology and 
hunting strategy for this group. We recommend 
the development of natural history studies as-
sociating direct observation to other methods 
(e.g., Global Positional System monitoring) 
for better understanding social relationships 
and interspecific interactions that may shape 
behavioral habits of South American canids.

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Messages In This Thread
Crab-eating Fox - Cerdocyon thous - by Taipan - 07-13-2018, 06:10 PM
RE: Crab-eating Fox - Cerdocyon thous - by Shenzi - 01-29-2019, 03:22 AM

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