Brief description
Resource owners generally win contests against intruders, a phenomenon referred to as the 'Owner Advantage' (OA). Uca mjoebergi is a typical fiddler crab that is highly sociable, territorial and lives in mixed sex colonies on intertidal mudflats. Burrows are used in territory defence, for mating, and as refuge from predators and environmental stresses. Fights are common between owners and floating males who battle for ownership of the territory and burrow. Experiments were conducted from 28th Sept - 30 Dec 2006 at the lower reaches of Ludmilla Creek within East Point Reserve, 5km North of Darwin, NT. Previous experiments have revealed that owners win more contests than floaters because they are more motivated. This experiment was designed to test if owners are more motivated than floaters in response to high quality territories. The results revealed that owners won more contests in 'high quality' territories than in 'natural' territories but this difference was not significant. Although owners win more contests in 'High quality' territories, the lack of significance may indicate only a small asymmetry between owners and floaters. It is possible that owners and floaters have similar abilities to perceive the food availability and be similar in motivational level.Lineage
Maintenance and Update Frequency: notPlanned
Statement: 'High quality' territories (n=25) and 'natural' territories were created in 0.5m x 0.5m plots on the mudflat. 'High quality' territories were manufactured by adding 3.5-4g powered fish food (OSI Marine Aquatic Flake Food and Aquasonic Complete Premium Marine Fish Food) dissolved in approx. 70ml of tap water. To the natural territories tap water only was added.
Treatments were applied to the plots and a 5cm margin around the outside to combat edge effects. Treatments were applied every day before low tide for three days before data collection.
Fights were documented between owners and floaters which were created by capturing owners from their burrows and releasing them into the plots. Plots were uncaged to ensure natural emigration and immigration but were temporarily caged during the release and fight with the owner. Cages were made from mesh (6.5cm wide, 0.8cm mesh size), and clear plastic strips lined the top 4.0cm of the cage on the inside and outside. Cages were dug 1-2cm into the mud. Only one fight was recorded per plot.
Floaters were released from shallow depressions dug in the mud. The depression was covered with a thin piece of plastic, which was weighed on top with mud and had fishing line attached to it. The fishing line was pulled from a distance exposing the depression and releasing the crab.
Major claw length (manus+pollex) and carapace width of each male were measured to the nearest 0.1mm using dial callipers. Fight duration was timed using a handheld stopwatch and recorded to the nearest 0.01s. This was measured after the event using a Sony Digital Video Camera.
Statement: A total of 50 fights were documented during this experiment. 25 fights occurred in the manufactured 'high quality territories', while 25 took place in 'natural territories.' A standard set of data was collected for each fight. For each fight the date, time, the type of floater, and winner were recorded. Additionally, all crabs were measured, and fight duration and phases recorded. The winner is the male that owns the territory at the end of a fight. The loser is the crab which walks away at the end of the fight. A fight was considered over when: a) the loser walked >30cm away, b) travelled past two other males territories, c) entered another burrow, or d) started another fight.
Parameters: Datatype (1=field, 2=video), encounter ID, date, plot number, ltidet (time of diurnal low tide), hightideht (high tide height of the tide which follows the diurnal low tide), rtimet (time of the fight), tsltide (number of minutes since low tide), ctype (condition, TE=owner within a plot with food added, TN=owner within a plot which is natural i.e. no food added), winner, cara (intruder carapace width - mm), chel (inturder cheliped / claw length - mm), ocara (owner carapace width - mm), ochel (owner cheliped / claw length -mm), actions observed, dura (duration of fight - seconds), digdura (dig duration - seconds), sizediff (size difference between owner and intruder claws - mm).
Notes
CreditFunded by The Ecological Society of Australia
Credit
Funded by The Australian Research Council (ARC)
Funded by The Australian Research Council (ARC)
Credit
The Australian National University (ANU)
The Australian National University (ANU)
Purpose
Previous experiments have revealed that owners win more contests than floaters because they are more motivated. This experiment was designed to test if owners are more motivated than floaters in response to high quality territories.
Previous experiments have revealed that owners win more contests than floaters because they are more motivated. This experiment was designed to test if owners are more motivated than floaters in response to high quality territories.
Issued: 06 08 2007
Data time period: 2006-09-28 to 2006-12-30
text: westlimit=130.5; southlimit=-13; eastlimit=131; northlimit=-12
text: uplimit=0; downlimit=0
Subjects
28960043 |
ANIMALS/INVERTEBRATES |
ARTHROPODS |
BIOLOGICAL CLASSIFICATION |
BIOSPHERE |
Biosphere | Ecological Dynamics | Competition |
Biosphere | Ecological Dynamics | Dominance |
COMMUNITY DYNAMICS |
Community Structure |
Crustaceans |
EARTH SCIENCE |
ECOLOGICAL DYNAMICS |
Fiddler crabs |
Owner Advantage |
Uca mjoebergi |
biota |
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Other Information
global : 637bba50-417e-11dc-aefb-00188b4c0af8
Identifiers
- global : a409e840-43d5-11dc-972b-00188b4c0af8
