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Intraspecific killing and cannibalismin adult Alpine marmots MarmotamarmotaC. Ferrari a c , C. Pasquaretta b , A. von Hardenberg c & B. Bassanoc

a Département des Sciences Biologiques, Université du Québec àMontréal, 8888 Montréal, Québec, H3C 3P8, Canadab Dipartimento di Biologia Animale, Università di Pavia, Via AdolfoFerrata 1, 27100, Pavia, Italyc Centro Studi Fauna Alpina, Parco Nazionale Gran Paradiso,Degioz 11, 11010, Valsavarenche (Aosta), ItalyPublished online: 19 Nov 2012.

To cite this article: C. Ferrari , C. Pasquaretta , A. von Hardenberg & B. Bassano (2012)Intraspecific killing and cannibalism in adult Alpine marmots Marmota marmota , Ethology Ecology& Evolution, 24:4, 388-394, DOI: 10.1080/03949370.2012.683454

To link to this article: http://dx.doi.org/10.1080/03949370.2012.683454

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Intraspecific killing and cannibalism in adult Alpine marmots Marmota marmota

Cannibalism, the consumption of individuals of the same species, associated withor without previous killing, is a widespread phenomenon across taxa, ranging fromprotists to vertebrates (FOX 1975a; POLIS 1981; ELGAR & CRESPI 1992). Episodes ofcannibalism have been reported in different contexts and various factors can increasethe rate of cannibalism in wild animals including food scarcity, overcrowding, stress,availability and behaviour of victims (FOX 1975a).

In free living rodents cannibalism on adult individuals is rare, while it has beenfrequently reported following infanticide (the killing of parental or nonparental young)(HARE 1991; VESTAL 1991). The predation hypothesis (the nutritional benefit obtainedby the cannibal) has been frequently suggested to explain this behaviour in rodents,since cannibalism appears to be negatively correlated with food availability (HOLMES

1977). However other hypotheses have been suggested to explain cannibalism andinfanticide in rodents and in other taxa: the resource competition hypothesis (HRDY

1979; EBENSPERGER & BLUMSTEIN 2007), the lifeboat hypothesis (POLIS 1980), thesexual selection hypothesis (EBENSPERGER 1998; WOODWARD et al. 2005). In the genusMarmota infanticide has been reported in Alpine marmot (Marmota marmota) (one casedirectly observed plus evidence of 13 other cases, COULON et al. 1995), golden marmot(Marmota caudata aurea) (indirect evidence of several cases, BLUMSTEIN 1997), yellowbellied marmot (two cases, one in captive animals, Marmota flaviventris) (BRODY &MELCHER 1985), while, to the best of our knowledge, cannibalism in wild populationshas been reported only in the yellow bellied marmot (three cases of adults consum-ing young, ARMITAGE et al. 1979). PLOTNIKOV (1997) reported 21 cases of cannibalismduring 4 years in the steppe marmot (Marmota bobak), but individuals were kept incaptivity and most episodes occurred on hibernating individuals. In this short note wereport the direct observation of an episode of intraspecific killing and cannibalism onan adult free-ranging Alpine marmot in the Italian Alps. We also report about a singularinjury found on the head a live trapped adult Alpine marmot, which presents similari-ties with the injury found on the cannibalized marmot and which probably caused thedeath of the marmot.

Episode of cannibalism in Alpine marmots

In 2006 we started a long term study on Alpine marmots in the North-WesternItalian Alps (Valsavarenche, Aosta, Gran Paradiso National Park, 45◦34’N/7◦11’E).During this ongoing project we marked 185 individual marmots and monitored18 family groups in the Orvielles study area, located at 2165 m a.s.l. (FERRARI et al.2009). In this context we observed one episode of intraspecific killing followed by

ISSN 0394-9370 print/ISSN 1828-7131 online© 2012 Dipartimento di Biologia Evoluzionistica dell’Università, Firenze, Italiahttp://dx.doi.org/10.1080/03949370.2012.683454http://www.tandfonline.com

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cannibalism on May 16th 2010. The study area was entirely covered by snow and inthe late morning, around 12:30 p.m., we saw a single marmot walking very close toour field-station; it was probably a dispersing individual looking for food or for a placeto stay since it walked and sniffed around without entering any burrow. The marmothad no ear tag but it was lacking fur over much of its body, which made it individuallyrecognisable. We hereafter refer to this marmot as “marmot A (MA)”. In the afternoonaround 3:00 p.m., from one of our observation points, we observed MA walking at adistance of 500 m from the field-station in an area inhabited by known family groups.The distance between us and MA was approximately 150 m and the visibility was per-fect. We observed the scene using two spotting scopes (Swarovsky 30 × 75). When MAapproached a burrow, two marmots emerged from it, came near MA and started anaggressive interaction. We recognised one of the two marmots as a well known markedadult male, hereafter called “MW”. The other was an unmarked adult individual that wewill hereafter call “MB”; we established that it was an adult as its size was comparableto that of MW, whose age was known. At first only MW chased and attacked MA, whotried to flee but was constantly followed and attacked by MW. After few minutes MBjoined the aggression and we started to see blood on the snow around the marmots.MW and MB were attacking MA who seemed unable to defend itself. This interactiondid not seem to be a normal agonistic interaction, in which usually the winner letsthe loser escape after a short chase (PERRIN et al. 1993a). It was rather a more violentoutburst characterised by intense chasing, biting and screaming. After approximately5 min MA was not trying to fight back or defend itself and MW and MB left and enteredthe nearest burrow, leaving MA alone in the snow. At this point we observed bloodtrails all around MA, who moved a few steps before remaining motionless on the snow.Few minutes later, MW and MB returned and started to feed on MA’s back. We clearlyobserved the two marmots feeding on the motionless body of MA (presumably alreadydead), and we took some pictures from our observation point. After few minutes thetwo marmots were probably disturbed as they returned to their burrow. We reachedthe site of the aggression and we collected the dead body of MA. We verified MA’s poorphysical condition with very little fur: a veterinary examination revealed that the lack offur was probably caused by Trichophyton sp. Fungi (E. FERROGLIO pers. comm.). Themarmot had a deep fresh hole in the head caused by a bite. Its back had a large, deepgash from where the other marmots had been feeding, removing major muscle parts toexpose the abdominal cavity (Fig. 1).

It is worth mentioning that on June 26th 2009, we captured a female adultmarmot (hereafter “MC”) that belonged to a known family together with one adult,untagged, male individual. During the days before the capture, we frequently observedaggressive interactions between the two individuals. When we captured the marmot,we noticed a deep hole in the head (clean and without blood). The marmot behavedin a particularly aggressive manner during the capture and we decided to release herwithout an ear tag after taking biometric measurements, to avoid touching her head.We saw marmot MC one more time the same day close to her burrow, but we neversaw her again during the same and the following seasons. We hypothesise that the maleindividual may have bitten the female during one of the aggressive interactions weobserved and that the female subsequently died, even if we cannot exclude the possibil-ity it dispersed away from her territory. Even though this wound presents similaritieswith the wound found on the cannibalized marmot described above (Fig. 2), we cannotexclude the hole was caused by the teeth or the claws of a predator, such as a Goldeneagle (Aquila chrysaetos), following a non fatal attack.

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Fig. 1. –– The cannibalized Alpine marmot in the snow right after the fatal aggression perpetrated bythe others two marmots in Orvieille, Gran Paradiso National Park (Aosta, Italy). Note the wound in theback where the aggressors were feeding from. Internal organs were visible. The marmot was probably adispersal individual in a poor body condition and it was lacking fur over much part of its body.

Discussion

Aggressive interactions for territorial defence are common in Alpine marmots andconsist mainly in chasing and biting (ZELENKA 1965; LENTI BOERO 2003). The rate andintensity of these interactions vary throughout the season according to dispersal rateand reproductive period (PERRIN et al. 1993b), but most of them are not fatal and donot injure seriously the opponent (C. FERRARI personal obs.). In May it is quite com-mon to observe agonistic interactions between dispersers, which attempt to conquera territory, and resident individuals, which defend their own territory from intruders(PERRIN et al. 1993b). Given the poor body condition of MA compared to that of MW,we do not believe that MA represented a real potential competitor for territory andmating. More likely, MA was a dispersing individual looking for food and the attackof MW and MB against him might have been induced by territorial defence of theoccupants and may have escalated to the killing and feeding on the victim (“territorial

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Fig. 2. –– Similarity between the wounds in the head of the marmot killed during the aggression (MA,Fig. 2a), and the adult live-trapped female (MC, Fig. 2b). The hole in the head of MA was possibly causedby a bite during the aggression. Note the similarities with the hole in the head of female MC: Even thoughwe cannot exclude that in the latter case it was caused by an eagle’s claw, it is plausible that this is themethod marmots use to seriously injure the opponent.

war” see HOLMES 1977; POLIS 1981). We can exclude parental defence as the causeof the killing, since the family group of MW and MB did not include other individu-als in 2010. It is worth noting that, even considering that violent aggressions betweenmarmots are frequent, cannibalism has never been reported in the species. Hereafterwe discuss some factors that could help in explaining this event. In the literature, foodscarcity is considered one of the main factors related to cannibalistic behaviour in nat-ural populations (FOX 1975a; POLIS 1981; GETTO et al. 2005; DUARTE et al. 2010). Theaccess to fresh protein is widely recognized as a mayor benefit of cannibalism, both interms of quality and quantity of food (LANE-PETTER 1968; POLIS 1980, 1981; GETTO

et al. 2005). Hibernating mammals, like the Alpine marmot, during particularly harshwinter may consume most or all their fat reserve so that at the vernal emergence theyrely completely on new food intake; But, especially at high altitude, a long lasting snowcover can delay the availability of food resource. In this situation the rate of aggressivebehaviours among individuals can increase, resulting in higher frequency of cannibal-istic behaviour (ARMITAGE 1975; FOX 1975a; HOLMES 1977). On May 12th 2010 thestudy area, unlike the same day of the previous 3 years, was still completely covered bysnow and marmots did not have access to food. We thus suggest that the necessity offresh food resource might have favoured the event of cannibalism.

In her review on cannibalism in natural population FOX (1975a, see also POLIS

1981) listed crowding as another factor potentially affecting cannibalistic behaviour,even when food was not a limiting element. High density, high production of youngand competition between females were suggested as factors potentially influencing thetwo episodes of adult cannibalizing young in the yellow bellied marmot (ARMITAGE

et al. 1979). Density of individuals and sex competition were probably not important inthe situation we observed, as few marmots were around at the time of the incident andyoung had not yet emerged.

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Availability of potential victims can promote the event of cannibalistic behaviourin natural populations (BROWER 1961; FOX 1975a, 1975b; ALABI et al. 2009).Accordingly to this, the presence of a vulnerable individual (MA) fighting against twohealthy individuals might have favoured the killing and the consumption of the victim,an event that possibly would not have happened if the intruder was in a better condition.

Finally the cannibalistic event seemed to be an opportunistic behaviour ratherthan an active “hunt”, since the two aggressors did not move from their territory butsimply attacked the intruder in their territory.

As MA and MC had wounds of similar dimension and position (Fig. 2) on thehead and based on the frequent observations of aggressive interactions in which thesetwo marmots were involved, we speculate that marmots possibly bite this way to kill orseriously damage each other during particularly aggressive interactions. Consideringthe position of the head wound it is unlikely that such a deep bite occurred by chanceduring an aggressive interaction, even though, in the case of MC, it is possible it resultedfrom causes other than intraspecific interaction.

In Alpine marmots, an herbivore species, cannibalism has to be considered a rarebehaviour but interestingly it might be an opportunistic strategy triggered by the socialbehaviour of the species and favoured by intrinsic and extrinsic factors. Further occa-sional data on the occurrence of such events and similar wounds, together with dataon the health and social rank of marmots involved in the interactions and about theenvironmental conditions at the time of the attacks, could improve our understandingof such behaviour.

Acknowledgments

We thank all the people and students who contributed to the project on the Alpine marmotsin the Gran Paradiso National Park (Italy) and A. Vik Stronen for comments on the first draft ofthe note. We thank all the park rangers, especially Martino Nicolino, Valter Vallet and StefanoCerise for their support and help in the field. This research is possible thanks to funds of the GranParadiso National Park. In 2010 Caterina Ferrari was supported by a “Bourse d’Excellence pourles Cycles Supérieurs de l’Université du Québec à Montréal (Canada)” and Cristian Pasquaretta bya doctoral grant of the University of Pavia (Italy). We thank two anonymous reviewers for theiruseful comments on the first version of this note.

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C. FERRARIDépartement des Sciences Biologiques, Université du Québec à Montréal, 8888Montréal, Québec H3C 3P8, Canada and Centro Studi Fauna Alpina, ParcoNazionale Gran Paradiso, Degioz 11, 11010 Valsavarenche (Aosta), Italy (E-mail:caterinaww@gmail.com).

C. PASQUARETTADipartimento di Biologia Animale, Università di Pavia, Via Adolfo Ferrata 1, 27100Pavia, Italy.

A. VON HARDENBERG and B. BASSANOCentro Studi Fauna Alpina, Parco Nazionale Gran Paradiso, Degioz 11, 11010Valsavarenche (Aosta), Italy.

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