Chemical substances produced by one species are sometimes found on the body of another species. Animals often ingest such foreign substances and sequester them into their integument, but here we ...report a case of direct application of heterospecific substances to the body. California ground squirrels,
Spermophilus beecheyi, and rock squirrels,
Spermophilus variegatus, apply scent derived from their major predator, rattlesnakes,
Crotalus spp., by chewing shed rattlesnake skins and licking their fur. We found that the sequence of body areas licked during application was essentially the same for the two species. We consider three hypotheses regarding the function of this ‘snake scent application’ (SSA): antipredator defence, ectoparasite defence, and conspecific deterrence. To test these hypotheses, we assessed patterns of species and sex/age class differences in application quantity and compared them with patterns reflecting differences in the importance of predation, flea loads and conspecific aggression as sources of selection. We found no species differences in application quantity; however, juveniles and adult females of both species engaged in longer bouts of application than adult males. This pattern of sex/age class differences in SSA supports only the antipredator hypothesis because juveniles are most vulnerable to predation and adult females actively protect their young. We found no evidence to support either the ectoparasite defence or conspecific deterrence hypotheses. Thus, SSA behaviour may be a novel form of chemical defence against predation.
Abstract
The purposes of this study were: (1) to describe the snake-directed antipredator behavior of rock squirrels; (2) to assess whether rock squirrels distinguish nonvenomous gopher snakes from ...venomous rattlesnakes; (3) to compare antisnake behavior in a snake-rare urban site and a snake-abundant wilderness site as a means of assessing whether natural selection or experience has generated population differences in behavior; (4) to assess snake densities in the two study sites; (5) to compare the antisnake behavior of rock squirrels with that of their closest relatives, California ground squirrels (Spermophilus beecheyi), a species that appears to differ from rock squirrels in exhibiting marked sexual-size dimorphism; and (6) to gather additional data on sexual size dimorphism in these two ground squirrel species. We tethered nonvenomous gopher snakes (Pituophis melanoleucus) and venomous western diamondback rattlesnakes (Crotalus atrox) in the field near burrows of marked squirrels and videotaped the ensuing interactions. Rock squirrels from both urban and wilderness populations confronted snakes while waving their fluffed tails from side to side, throwing substrate at the snakes, and even attacking snakes on occasion. Survey data confirmed large differences in snake densities between the two sites. Squirrels from the snake-abundant wilderness site distinguished rattlesnakes from gopher snakes, but squirrels from the snake-rare urban site did not. Since these squirrels show similar evidence of selection from snakes, as revealed by their equivalent physiological resistance to rattlesnake venom, we attributed these behavioral differences to the effects of snake experience. Rock squirrel antisnake behavior was very similar to that of California ground squirrels. Where the two species' behavior was dissimilar, the differences may be due in part to the interspecies variation in sexual size dimorphism confirmed in this study, and to the greater number of rattlesnake species that rock squirrels encounter.
Chemical substances produced by one species are sometimes found on the body of another species. Animals often ingest such foreign substances and sequester them into their integument, but here we ...report a case of direct application of heterospecific substances to the body. California ground squirrels, Spermophilus beecheyi, and rock squirrels, Spermophilus variegatus, apply scent derived from their major predator, rattlesnakes, Crotalus spp., by chewing shed rattlesnake skins and licking their fur. We found that the sequence of body areas licked during application was essentially the same for the two species. We consider three hypotheses regarding the function of this 'snake scent application' (SSA): antipredator defence, ectoparasite defence, and conspecific deterrence. To test these hypotheses, we assessed patterns of species and sex/age class differences in application quantity and compared them with patterns reflecting differences in the importance of predation, flea loads and conspecific aggression as sources of selection. We found no species differences in application quantity; however, juveniles and adult females of both species engaged in longer bouts of application than adult males. This pattern of sex/age class differences in SSA supports only the antipredator hypothesis because juveniles are most vulnerable to predation and adult females actively protect their young. We found no evidence to support either the ectoparasite defence or conspecific deterrence hypotheses. Thus, SSA behaviour may be a novel form of chemical defence against predation. PUBLICATION ABSTRACT
I tested two models (pair bonding; coyness) of the relationship between duetting and pair bonding with behavioral and vocal data from captive canary-winged parakeet (Brotogeris v. versicolurus) mates ...before and after their pair formations. In all pair formations, pair establishment preceded or occurred simultaneously with well-coordinated, species-typical duets. There was no evidence of duet practise before pair initiation or improvement in duets during pair integration. Both models lead to the prediction that new pairs should duet more frequently early in their pairing compared to later. But duetting rates did not exhibit a peak early in the pair relationships. New pair duet rates increased relatively late (third to fourth week after pairing) in the pair history and did not show a decline over time. Affiliative interactions did not peak at the same time as duetting, as predicted by the pair-bonding model, nor did affiliative acts peak after a peak in duetting, as in the coyness model. Duetting rates of new pairs were not significantly different from those of older pairs. Thus, although duetting is a cooperative, intrapair interaction, there is no evidence that it promotes pair bonding in canary-winged parakeets. A significant, positive correlation was found between duets and agonistic acts against others. The pair formation data and this correlation between duetting and agonism against others suggest that there has been selection for rapid acquisition of duetting ability with a new partner. If parakeet pairs spent prolonged periods learning their duets, they could lose status within the group and the ability to present a coordinated, united front in the competition for resources. This may have been the selection pressure that led pairing in canary-winged parakeets to be accomplished without recourse to coy behavioral or vocal strategies. /// Ich habe zwei Muster (Paarbindungs- und Sprödigkeitsmuster) hinsichtlich des Verhältnisses zwischen Duettgesängen und Paarbindungen anhand Verhaltens- und Duettdaten von Brotogeris v. versicolurus (Canary-winged parakeet)-paaren vor und nach Paarbildung im Labor nachgeprüft. In sämtlichen Sittichpaarbildungen geht die Paarbildung allen anderen Handlungen voran oder findet gleichzeitig mit für diese Vogelart typischen Duettgesängen statt. Es besteht daher kein Beweis entweder für das Vorhandensein von Duettgesängen vor der Paarinitiation oder für eine Verbesserung der Duettgesänge während der Paarintegration. Beide Muster weisen darauf hin, dass neue Paare im Vergleich zu älteren Paaren eigentlich häufiger duettieren sollten. Die Duettwerte weisen früh im Paarverhältnis jedoch keinen Höchstwert auf. Duettwerte neuer Paare steigen verhältnismässig spät (in der dritten bzw. vierten Woche nach der Paarbildung) an und weisen kein zeitbedingtes Absteigen auf. Affiliative wechselseitige Handlungen erreichen gleichzeitig mit dem Duettieren keinen Höchstwert, wie dies im Paarbindungsmuster gezeigt wird, und die affiliativen Handlungen erreichen auch nach dem Höchstwert beim Duettieren keinen Höchstwert, wie im Falle des Sprödigkeitsmusters. Duettwerte neuer Paare weichen nicht besonders von denen älterer Paare ab. Daher, obwohl das Duettieren eine kooperative, zwischen Paarpartnern stattfindende Handlung ist, kann kein Beweis dafür geliefert werden, dass solches Duettieren die Paarbindung bei dieser Sittichart fördert. Eine positive, signifikante Korrelation zwischen Duettgesängen und agonistischen Handlungen anderen gegenüber wird festgestellt. Die Paarbildungsdaten sowie diese positive Korrelation zwischen Duettieren und Agonismus anderen gegenüber lassen auf einen selektionsbedingten schnellen Erwerb dieser mit neuen Partnern einhergehenden Duettfähigkeit schliessen. Verbrächten die Sittiche längere Perioden damit, ihre Duettgesänge zu erlernen, könnten sie ihren Status innerhalb der Gruppe sowie ihre Fähigkeit verlieren, eine koordinierte, vereinigte Front bei der Konkurrenz um Nahrungsquellen zu machen. Letzteres kann daher der Selektionsdruck gewesen sein, der bei dieser Sittichart zur Paarung ohne Rückgriff auf das Sprödigkeitsverhalten oder vokale Strategien geführt hat.
The copulatory vocalizations of female baboons (Papio ursinus) are more complex than those of female gibbons (Hylobates hoolock) or human females. Adult males of all these species begin calling later ...than the female, but subordinate baboon males do not call. Copulatory vocalizations may serve to mutually stimulate the mating partners or to incite male competition.
This paper describes the construction and use of a new Burrowing Owl (Speotyto cunicularia) trap. Advantages of this new trap include its effectiveness in even the most inaccessible burrows, its ...safety to the owl(s) contained within, its cryptiveness when in place (making it tamper proof, an important consideration when trapping owls in urban settings), the ease of removal of captured owls through a hinged access door, its ease of transport to study sites, its low cost, the ability to check its contents via a clear Plexiglas door, and the possibility of catching owls or other fossorial animals either as they exit or enter burrows. This new trap has been used for 2 yr in southern New Mexico with a success rate of 75%. /// En este trabajo se describe la construcción y uso de una nueva trampa para atrapar individuos de Speotyto cunicularia. Las ventajas de esta nueva trampa incluyen su efectividad, inclusive en las madrigueras o cuevas más inaccesibles, seguridad, hacia los buhos que caigan en estas, secretividad (críptica), facilidad para remover los animales capturados, facilidad de transporte a las áreas de estudio, bajo costo, facilidad para cotejar lo que hay dentro de esta (a través de una puerta de plástico transparente), y posibilidad de atrapar animales que viven en madrigueras cuando éstos entran o salen de las mismas. Este nuevo tipo de trampa ha sido utilizado por dos años en Nuevo México con un éxito de atrapamiento de 75%.
