A field study investigating effects of landmarks on territory size and shape

Abstract

Few studies have examined how landmarks affect territories' fundamental characteristics. In this field study, we investigated effects of landmarks on territory size, shape and location in a cichlid fish (Amatitlania siquia). We provided cans as breeding sites and used plastic plants as landmarks. During 10 min trials, we recorded locations where residents chased intruders and used those locations to outline and measure the territory. In two experiments, we observed pairs without landmarks and with either a point landmark (one plant) or linear landmark (four plants) placed near the nest can. We alternated which trial occurred first and performed the second trial 24 h after the first.Territories were approximately round without landmarks or with a point landmark but were significantly more elongated when we added a linear landmark. Without landmarks, nests were centrally located; however, with any landmark, pairs set territory boundaries closer to the landmark and thus the nest. Territory size was significantly reduced in the presence of any landmark. This reduction suggests that a smaller territory with well-defined boundaries has greater benefits than a larger territory with less well-defined borders.

The Effects of Landmarks on Territorial Behavior in a Convict Cichlid, Amatitlania siquia

“…The decrease in territory size observed with the increase in the landmarked boundaries indicates that it may be beneficial to defend a smaller territory with well‐defined boundaries rather than a larger territory with undefined borders. A similar reduction in territory size in the presence of landmarks has been reported in previous laboratory experiments (Van den Assem ; LaManna & Eason ) as well as in some field studies (Kodric‐Brown ; Suriyampola & Eason ). Convict cichlids may use landmarks both as spatial mapping cues during navigation and to determine the exact location of the territory boundary.…”

“…A number of previous studies suggest that territorial animals tend to establish territories so that boundaries are situated at conspicuous features of the habitat (Kodric‐Brown ; Kruuk ; Reid & Weatherhead ; Eason et al. ; LaManna & Eason ; Suriyampola & Eason ). Such landmarks clearly define territory boundaries and may lower defense costs by allowing residents to easily determine when another individual has intruded, reducing error in judging the location of the boundary that could lead to accidental intrusions by neighbors, and reducing time and energy spent in patrolling borders (Eason et al.…”

“…Little attention has been given to the effects of landmarks on fundamental territory properties such as size and shape. Although resource distribution and defensive costs were long ago identified as primary determinants of optimal territory size (Schoener ), some studies have also shown that landmarks may reduce the size of territories (Baylis ; Kodric‐Brown ; LaManna & Eason ; Suriyampola & Eason ). Similarly, despite the generally accepted idea that round territories are optimal (Andersson ; Dill ; Hixon ; Adams ), some studies suggest that landmarks and uneven topography can affect optimal territory shape (Eason ; Suriyampola & Eason ).…”

“…Finally, a previous manipulative field experiment revealed that A. siquia pairs responded strongly to the presence of landmarks. In that experiment, pairs were provided with artificial nest sites (opened cans) on a flat sandy substrate without natural landmarks (Suriyampola & Eason ). When plastic plants that served as landmarks were placed near the nest, pairs defending territories in areas without landmarks shifted boundaries in response to the presence of landmarks, altering territory size and shape (Suriyampola & Eason ).…”

In Space and Time: Territorial Animals are Attracted to Conspecific Chemical Cues

“…For example, in some species, residents able to hold territories gain reproductive advantages over non-residents (Bergman et al 2007; Kresnik & Stutchbury 2014), and different levels of motivation among these competitors can lead to predictable contest outcomes (Bergman et al 2010). Territorial dimensions can shift with the availability of landmarks (Heap et al 2012; Suriyampola & Eason 2014), and threats produced by non-residents in more highly valued areas of a home range can be more likely to elicit resident responses relative to other areas (Furrer et al 2011). Additionally, seasonal changes in receiver physiology alter sensory sensitivity (Saveer et al 2012; Dey et al 2015).…”