Intrusion Experiments to Measure Territory Size: Development of the Method, Tests through Simulations, and Application in the Frog Allobates femoralis

Abstract

Territoriality is a widespread behaviour in animals and its analysis is crucial in several areas of behavioural, ecological and evolutionary research. Commonly, territory size is assessed through territory mapping and the application of simple area estimators such as minimum convex polygons. In the present study we demonstrate that territory size can be determined adequately with an active approach through intrusion experiments, a technique that is commonly used in behavioural research in other contexts. Tests with simulated data indicate that a minimum of twelve trials needs to be performed to establish reliable orders of relative territory size. To estimate absolute territory size, detailed hull techniques are most appropriate when analyzing point patterns of intrusion experiments, while the local convex hull estimator enables the construction of internal utilization distributions based on such point patterns. Additionally we suggest a ‘stretch the centre’ approach to emphasize the actual process of intrusion experiments in the construction of internal utilization distributions. To demonstrate the utility of the method, we apply all findings from the simulations to data from fieldwork with the model species Allobates femoralis, a territorial aromobatid frog from the lowland rainforest of French Guiana.

Relying on known or exploring for new? Movement patterns and reproductive resource use in a tadpole-transporting frog

“…Allobates femoralis is a small diurnal frog (snout-urostyle length approximately 25 mm) common throughout Amazonia and the Guiana Shield ( Amézquita et al, 2009 ). During the rainy season males occupy territories (average defended area: 151.13 m 2 ( Ringler et al, 2011 )) which they advertise by calling and defend for up to several months ( Roithmair, 1992 ; Ringler, Ursprung & Hödl, 2009 ). Mating and oviposition of approximately 20 eggs take place in the leaf litter inside the male’s territory ( Roithmair, 1992 ; Ringler et al, 2012 ).…”

Brood-partitioning behaviour in unpredictable environments: hedging the bets?

“…Males of the Neotropical frog A. femoralis (Boulenger 1884 ; Anura: Dendrobatidae) are highly territorial and announce territory possession by a prominent advertisement call (Narins et al 2003 ; Ringler et al 2011 ). Females are inter-dispersed between male territories and show non-aggressive site fidelity (Ringler et al 2009 , 2012 ).…”

Spatio-Temporal Characteristics of the Prolonged Courtship in Brilliant-Thighed Poison Frogs, Allobates femoralis

“…femoralis males whereas the estimated peripheral territory represented the area which we expect males to defend from conspecific males (cf. Ringler et al 2011). We used only those males for which we recorded a minimum of five catching points for this analysis and used only those points where the males were observed calling or approaching the simulated call emitted from the loudspeaker.…”