Indirect measures of reproductive effort in a resource-defense polygynous ungulate: territorial defense by male guanacos

Abstract

Trade-offs between reproductive effort and activities that are likely to enhance survival have been studied extensively in harem defense ungulates. However, among resource defense systems, ecological determinants of the variation in male reproductive effort are less understood. The aim of this study was to assess the extent of the effort devoted to territorial defense by male guanacos and how this is affected by predation risk. Time allocation to different activities and displays of aggressive behavior were compared between territorial and bachelor male guanacos within two populations with contrasting levels of predation risk. Territorial males devoted almost twice the time than bachelors to vigilance and moving, at the expense of foraging time. Aggressive interactions were more frequent and severe for territorial males than for bachelors, based on observation. These differences were larger during the reproductive season but remained statistically significant after this period, highlighting the extended effort towards territorial defense beyond the peak of reproductive activity. In contrast to previous observations on females of the same populations, there was no effect of predation risk level or group size on male time allocation, suggesting that under the ecological conditions of the study, intra-sexual competition entails a stronger influence on male individual behavior than predation risk level.

Dung odours signal sex, age, territorial and oestrous state in white rhinos

“…They did this by increasing their visitation to the midden and reducing their latency in assuming a vigilance posture. Increasing midden visitation probably allows territorial males the opportunity to reassess the odour and the presence of the rival [57,58]. Shorter latency in assuming a vigilance posture, however, permits the territorial males to prepare for a potential aggressive encounter with another male [58].…”

The composition and function of all‐male herds of Thornicroft's giraffe, Giraffa camelopardalis thornicrofti, in Zambia

“…Temporary all‐male groups have been observed in ungulates (Estes, ; Rubenstein & Hack, ; Marino, ), elephants (Evans & Harris, ; Chiyo et al ., ; Lee et al ., ), cetaceans (Moller et al ., ; Whitehead, ; Wiszniewski, Brown & Moller, ), primates (Hrdy, ; Grueter, Chapais & Zinner, ; Pappano et al ., ) and carnivores (Packer & Pusey, ; Caro, ; Durant et al ., ; Hirsch et al ., ). All‐male groups are a characteristic of sexual segregation (Ruckstuhl & Neuhaus, ), but factors promoting sexual segregation need not be identical to those favouring the establishment of temporary units consisting only of males.…”

“…All‐male groups could provide a venue for adolescent males to practice fighting skills before engaging in intensive male–male combat over access to oestrous females [giraffes, Estes, ; African elephants, Loxodonta africana , (Chiyo et al ., )] or to establish stable rank hierarchies during the nonmating season as a means of reducing conflict costs over oestrous females [raccoons, Procyon lotor , (Gehrt, Gergits & Fritzell, )]. Younger males could associate with older males to learn more about resource distribution [sperm whales, Physeter macrocephalus , (Whitehead, ); African elephants, (Evans & Harris, , ; Chiyo et al ., )] or male subgroups could reduce the chances of predation [zebra, Equus burchelli , (Rubenstein & Hack, ; guanaco, Lama guanicoe , (Marino, )]. All‐male groups composed of similar‐aged individuals could form as a foraging strategy due to size‐related energetic requirements [bighorn sheep, Ovis canadensis , (Ruckstuhl, )].…”

Factors influencing reproductive success in male white‐tailed deer

“…The relative importance of age, body size, and antler and horn size as determinants of male reproductive success varies between ungulate species (Clutton‐Brock et al , Hogg and Forbes , Coltman et al , McElligott et al , Willisch et al ). Male polygynous ungulates exhibit a variety of mate guarding behaviors, including resource defense, harem defense, lekking, and tending, and the adopted behaviors influence the role of male traits in reproduction (Hogg , Clutton‐Brock et al , Clutton‐Brock , Marino , Ciuti and Apollonio ). For example, reproductive success in populations of red deer that exhibit harem‐defense behaviors is almost entirely restricted to a relatively small group of prime‐aged, harem‐holding males that have large bodies and antlers (Clutton‐Brock et al , Pemberton et al ), whereas reproductive success is attributed to a larger group of males possessing a variety of body and horn sizes in bighorn sheep that employ tending, coursing, and blocking behaviors (Hogg , Hogg and Forbes ).…”