U. pugilator, Photo by Madison Pechulis licensed under CC BY-NC-ND 4.0

Intraspecific vs Interspecific Competition Between Fiddler Crabs

Treatment 1 = intraspecific competition within species 1 (U. pugilator)

Treatment 2 = intraspecific competition within species 2 (U. panacea)

Treatment 3 = interspecific competition between species 1 and species 2

Treament 1ExtendManus AlignDactyl SlideInterlace
Trial 1281332
Trial 24226111
Trial 3281183
Standard Deviation8.18.14.01
Standard Error4.
Treatment 2ExtendManus AlignDactyl SlideInterlace
Trial 123939
Trial 2421362
Trial 323982
Standard Deviation10.
Standard Error6.
Treatment 3ExtendManus AlignDactyl SlideInterlace
Trial 141261311
Trial 23711125
Trial 345301710
Trial 43121129
Trial 533172019
Trial 641271519
Standard Deviation5.
Standard Error2.
F- value1.433.159.945.78

Treatment Averages

ExtendManus AlignDactyl SlideInterlace
Intraspecific Species 132.616.67.32
Intraspecific Species 229.310.35.64.3

Post-hoc Tukey Tests

F-valueP-valueTukey Test
Dactyl Slide treatment 1&35.781530.0.031710.1667
Interlace treatment 1&39.9436740.02477.5
Interlace treatment 2&399436740.00839.1667
Photo by Madison Pechulis licensed under CC BY-NC-ND 4.0

This is how we set up the dividers in each tank using plexiglass and laminated sheets of paper.

Photo by Madison Pechulis licensed under CC BY-NC-ND 4.0
Photo by Madison Pechulis licensed under CC BY-NC-ND 4.0

General Observations:

  • U. pugilator is larger and pinker/brighter in pigment than U. panacea
  • Most individuals like to spend more time in the salt water versus the damp sang area
  • Individuals eat the dried shrimp typically within a day, but they do not initially go after it right away
  • Initial plastic dividers were not effective in dividing individuals in both tanks, switched to using harder waterproof plastic
  • Most of the time spent in Tank 3 is spent climbing over each other in the corners of the tank
  • Many of the pinching is done with their little claw versus their big claw.
  • Appears as if they have difficulty opening their big claw 
  • One individual from Tank 1 died after the first day