Territories 1 Flashcards
Social relationships may lead to aggregation or spacing out and territorial behaviour
Aggregation & territoriality are linked as part of a continuum. Spacing does not necessarily imply territorial behaviour and can be due to habitat structure or chance mortality.
General definition of territoriality
when individuals or groups occupying a suitable habitat, space themselves out more than would be expected by chance (or as a passive product of habitat structure or non-random mortality.)
e.g. territoriality has led to regular spacing of gannet nests within breeding sites which prevents neighbours from pecking oneanother
Territoriality is the behaviour related to the defence of a territory against intruders.
Definition of home range
The area encompassing an animal’s typical daily behaviours (feeding, resting, reproduction, shelter-seeking etc) in which an animal spends most of its time. This is the area that yiou measure to estimate territories. It excludes dispersal & migration behaviour
Definition of territory
An area within the home range occupied more or less exclusively by an animal or group of animals of the same species & held through overt defence, display or advertisement.
Territory may be only part of the home range.
But: how exclusive & for how long??
Results from extreme asymmetric competition – ‘winners’ and ‘losers’
Types of territorial defence
(see level 1)
overt aggression
`keep out’ signals (e.g: song, odour cues etc.)
Quantifying home range/ territories
Estimates depend on how long / frequently the animal’s locations are recorded. Radiotagging is effective for this but only suitable for longer living larger organisms. Triangulate to estimate locations. to estimate locations. Asymptote eventually reached.
It is essential to check the location of animals at different times of the day (diel)/ year cycle as this will impact where individuals are found e.g. badgers need to be monitored at night as they forage nocturnally, location recording during the day
Methods of quantifying home range/ territories
Radiotagging can be used to observe large ungulates allowing us to follow movement over seasons between localities. e.g. Temporal components of home ranges as seen in wildebeest: Nov-April small range, May-June other area used – different home ranges? Cyclical migration?
Polygon methods. E.g. minimum convex polygons
Probability distribution methods. E.g. kernel estimators
Hotspots are dens, refuges, water holes, feeding patches or nests (in birds)
Identify these core sites via observation from hides or camera trap
Areas of intensive use aka ‘core areas’ may or may not = territories
Territory structure: territories are dynamic
They can change in size & shape with season, population density, age or other factors
*e.g: N. American dunlin (Calidris alpina) bird populations(Holmes 1970)
Observed to utilise small territory when population density high (Kolomak, Ukraine)
And also large territory with `buffer zones' in low density (Barrow, Canada?)
Pattern of space use within territory may change as it expands or contracts
e.g: Tree sparrows (Spizella arborea)
– use whole of territory with equal intensity when it is fully contracted
– use only central area intensively when it is expanded
Example of space pattern: Hexagonal territories used by mouth brooding cichlid maximise space usage and leave no gaps
E.g: can be observed in mouthbrooding cichlid (Tilapia mossambica)
borders of male territories = sandy ridges surrounding each owner
Males (black individuals on pic) brood the eggs and hatched young in their mouths
Why defend a territory
There are costs: Defence is a cost on the owner, it requires:
time, energy & potentially injury as a cost of fighting. Ownership signals also increase conspicuousness increasing the risk of predation.
There are also many potential benefits: food, mates, shelter, nesting sites,
sun lit rocks for reptilesetc.
(overall: to improve fitness benefit)
Why aren’t all animals territorial?
Are herbivores less likely to have territories?
Reasons for territory defence : Food benefit : resource dispersion hypothesis
Hypothesis has been tested by manipulation experiments in white wagtails (Motacilla alba alba) (Zahavi 1971)
When food is provided in small clumps individuals defend it aggressively
Whereas when food is spread out individuals fed together in ‘peaceable’ flocks.
Blackbird (Turdus merula) conspecific territory competition (Cresswell 1997)
Reduction in feeding efficiency can be observed in blackbirds due to distraction by multiple conspecifics due to interaction or even without
Behaviour supporting this hypothesis has been observed in social primates
e.g. : social primates (Johnson et al. 2002).
Spatial &/or temporal distribution & availability of food was observed to effect territory size.
Species with a foliage diet had smaller territories than fruit eating species. This is likely due to the fact that fruit is more sparsely distributed requiring more space and time to forage for than foliage.
Territory function/ benefits: Mates
often related to food availability.
Males with good territories can acquire more females than males with poorer territories.
Sometimes mating preferences are based on availability of suitable breeding sites, or protection from predators.
Note: Leks (gatherings of adult migratory animals to mate) have no resources at all, female preference depends solely on the quality of the male.
Other territory benefits
reduced cannibalism of offspring by neighbours
access to safe roosting sites
In reptiles - access to sunning areas for thermoregulation
