Individual variation in the dear enemy phenomenon via territorial vocalizations in red squirrels

Territoriality arises when the benefits of resources exceed the costs of defending them. The dear enemy phenomenon, where familiar territorial neighbours refrain from intruding on one another and mutually reduce their defensive efforts, allows for reduction of these costs but requires discrimination between conspecifics. We hypothesized that territorial vocalizations in red squirrels (Tamiasciurus hudsonicus) are used for this discrimination. We performed a speaker replacement experiment where red squirrels () were temporarily removed from their territories and replaced with a speaker broadcasting their own call, an unfamiliar call, or silence. Contrary to our prediction, there were no differences in overall intrusion risk among our three playbacks, but the identity of intruders did vary. Existing variation in familiarity within territorial neighbourhoods should be considered, rather than the binary classification of familiar or stranger, when studying dear enemy effects. We also discuss the variable importance of silence in acoustic territorial populations.

Do olfactory behaviour and marking responses of Konik polski stallions to faeces from conspecifics of either sex differ?

The aim of the study was to assess whether adult stallions differentiate their olfactory and marking behaviour towards the excreta of their potential male rivals and mares. Four Konik polski stallions were individually exposed simultaneously to their own and each others' faeces as well as faeces of mares in oestrus vs. dioestrus. Five series of 30min observation sessions were conducted in a round pen each on two consecutive days from March to July, totaling in 5h observation per stallion. Stallions sniffed and displayed flehmen reaction towards mares' faeces significantly longer (P<0.01) than towards stallions' faeces. No significant differences were found in marking by defecations upon stallions' vs. mares' faeces. The stallions urinated exclusively on mares' faeces. Sniffing, flehmen, defecations and urinations performed towards faeces of mares in oestrus vs. dioestrus did not differ significantly. The results showed that stallions differentiate their olfactory behaviour towards excreta of conspecifics of different sex but perhaps not towards faeces of females in different reproductive status. This for the first time establishes that stallions exhibit different marking behaviour upon stallions' vs. mares' faeces. It is hypothesized that marking of other stallions' faeces by defecation may advertise presence of the stallion, whereas marking of mares' faeces by urination may serve to mask the presence of a mare to prevent potential rivals from locating the mare in an area where mares' faeces are found.

Consequences of animal interactions on their dynamics: emergence of home ranges and territoriality

Animal spacing has important implications for population abundance, species demography and the environment. Mechanisms underlying spatial segregation have their roots in the characteristics of the animals, their mutual interaction and their response, collective as well as individual, to environmental variables. This review describes how the combination of these factors shapes the patterns we observe and presents a practical, usable framework for the analysis of movement data in confined spaces. The basis of the framework is the theory of interacting random walks and the mathematical description of out-of-equilibrium systems. Although our focus is on modelling and interpreting animal home ranges and territories in vertebrates, we believe further studies on invertebrates may also help to answer questions and resolve unanswered puzzles that are still inaccessible to experimental investigation in vertebrate species.

How to identify dear enemies: the group signature in the complex song of the skylark Alauda arvensis

Song geographic variation and Neighbour–Stranger (N–S)discrimination have been intensively but separately studied in bird species,especially in those with small- to medium-sized repertoires. Here, we establish a link between the two phenomena by showing that dialect features are used for N–S recognition in a territorial species with a large repertoire, the skylark Alauda arvensis. In this species, during the breeding season, many pairs settle in stable and adjoining territories gathered in locations spaced by a few kilometres. In a first step, songs produced by males established in different locations were recorded, analyzed and compared to identify possible microgeographic variation at the syntax level. Particular common sequences of syllables (phrases) were found in the songs of all males established in the same location (neighbours), whereas males of different locations (strangers) shared only few syllables and no sequences. In a second step, playback experiments were conducted and provided evidence for N–S discrimination consistent with the dear-enemy effect,i.e. reduced aggression from territorial birds towards neighbours than towards strangers. In addition, a similar response was observed when a `chimeric'signal (shared phrases of the location artificially inserted in the song of a stranger) and a neighbour song were broadcast, indicating that shared sequences were recognized and identified as markers of the group identity. We thus show experimentally that the shared phrases found in the songs of neighbouring birds constitute a group signature used by birds for N–S discrimination, and serve as a basis for the dear-enemy effect.