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Food preference in land hermit crabs ( Coenobita sp.) when given choice of meat or vegetables. Whitney Jardine , Sarah Park and Nataya Smith BIOL 3401 Mount Allison University November 22, 2013. Hermit Crabs. Land hermit crabs ( Coenobita sp.) G astropod shells for protection
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Food preference in land hermit crabs (Coenobita sp.) when given choice of meat or vegetables Whitney Jardine, Sarah Park and Nataya Smith BIOL 3401 Mount Allison University November 22, 2013
Hermit Crabs • Land hermit crabs (Coenobita sp.) • Gastropod shells for protection • Scavengers • Locate food by olfaction
Purpose • To determine food preference in hermit crabs when given choice between meat and vegetables
Previous Studies • Visually orient food and conspecifics for social facilitation of foraging (Kurta 1982) • Wide array of food (fruit, leaves, dead animals,etc.) (Burggren & McMahon 1988; Brightwell 1950)
Previous Studies • Optimal foraging theory: scavengers selecting nutritionally balanced diet (Stephens & Krebs 1986) • Negative preference induction (Thacker 1996) • King crab, Asian shore crab, squat lobster and crayfish found to prefer meat diet (McLaughlin & Hebard 1959; Brousseau & Baglivo 2005; Karas et al. 2007; Correia 2003)
Hypotheses • Spend greatest proportion of time in meat zone • More likely to spend more time in the zone with conspecifics
Method • 11 land hermit crabs • Starved for 4 days prior to study • Testing done in evenings with overhead lights off • 1 red lamp between two testing tanks • Tanks divided into three zones
Method • Hamburger, chicken, ham, and tuna in meat zone • Spinach, carrot, lettuce, asparagus in vegetable zone • Crabs were placed in center of tank and gave them 2 minutes for acclimation • Observed for 15 minutes, recording location every minute
Method • Individual trials once with each crab • 4 group trials • Cleaned tank between each trial • Switch food to opposite ends for half of trials
Results Figure 1: Mean percent time spent in each tank section across 11 individual hermit crab trials (n=11). Each trial lasted 15 minutes.
Results Figure 2: Mean percent time spent in each tank section across 4 group trials (n=11). Each trial lasted 15 minutes.
Results Table 1: Results of chi square test for differences in percentage of time spent in each zone (meat, no food, vegetable) Critical value 5.99.
Discussion • More time was spent in the vegetable zone than meat zone for individual and group trials • Did not support our first hypothesis (choosing meat over vegetables) • Did support our second hypothesis (social foraging)
Discussion • Non-significance likely due to no food zone • Different species of crab than previous studies • Negative preference induction • Vegetables easier to ingest quickly • Benefits of social foraging