Reading 2.2 Deal 2017

Question 1

What were the three hypothesis being tested?

Answer 1

• To examine the effect of perceived predation risk on filial cannibalism in the sand goby by comparing the behaviour of egg-tending males exposed to a perch (predator) with males guarding eggs in a safe environment
  • The effect of predation threat on nest construction
  • Motives behind filial cannibalism eg to acquire energy for nest maintenance and construction

Question 2

The study methods

Answer 2

• Perch were unfed throughout
  • Male female pairs were chosen and added to an aquarium with a nesting compartment (opaque Plastic barrier) and an exposure compartment (clear plastic barrier
  • Male was encouraged to start nest production by being in the nest compartment
  • Females were released into the sea
  • Eggs were given to male and he was assigned either predator or control treatment
  • Perch was then added to predator and in control a plastic plant was added
  • Transparent barrier separated tanks
  • Dissolved oxygen was measured to prevent it influencing cannibalism rate (Klug et al 2006)
  • Final sample excluding gobies that died was 33 predator treatment males and 31 control males

Question 3

What is one factor that had to be controlled to prevent it influencing cannibalism rate?

Answer 3

Dissolved oxygen, Klug et al 2006

Question 4

Male weight change

Answer 4

• Tested whether mode of filial cannibalism in isolation influenced weight change
  • The model of filial cannibalism and number of eggs consumed and this interaction was measured

Question 5

Nest construction and maintenance

Answer 5

• Nest architecture, opening height and nest sand pile height effect on predation treatment, male body condition

Question 6

Study Results

Answer 6

• All males consumed some eggs (minimum of 120)
  • 18/64 engaged in total filial cannibalism
  • Small initial clutches were more likely to engage in total filial cannibalism
  • Body condition and dissolved o2 had no effect on total filial cannibalism

Question 7

How many fish engaged in total filial cannibalism?

Answer 7

18/64

Question 8

What size was most likely to engage in total filial cannibalism?

Answer 8

Small

Question 9

Did body condition have an effect on total filial cannibalism?

Answer 9

No

Question 10

Did dissolved O2 have an effect on total filial cannibalism?

Answer 10

No

Question 11

Partial filial cannibalism

Answer 11

• No predictors had significant effects on the number of eggs eaten
  • Predictors include predation treatment, pre spawning male body condition and dissolved O2
  • Males lost significantly less weight with an increased number of eggs consumed

Question 12

Did males lose or gain weight with an increased number of eggs consumed?

Answer 12

Lost significantly less

Question 13

Height and width of nest entrances was… to the predation treatment among partial filial cannibals

Answer 13

Unrelated

Question 14

Among total filial cannibals perch exposure was associated with…?

Answer 14

Significantly taller and wider nest entrances

Question 15

Results in accordance with the hypothesis P1

Answer 15

• Partial filial cannibalism was not influenced by the presence of a predatory perch
  • Males tended to consume their entire brood less often in the presence of a perch in tfc
  • Results suggest threat of predation may have a more prominent effect on filial cannibalism

Question 16

Results in accordance with the hypothesis P2

Answer 16

• Side blotched lizard females that are injured and cannot evade predators elevate their level of parental expenditure on current offpsring fox and mccoy 2000
  • No evidence that energy from egg consumption was used for nest construction

Question 17

Results in accordance with the hypothesis P3

Answer 17

• Factor most strongly influencing the occurrence of total filial cannibalism was clutch size
  • Small clutch size meant more cannibalism
  • Benefits must outweigh costs when brood is small

Question 18

Conclusions

Answer 18

• Partial filial cannibalism was not affected by the perceived threat of predation to the parent
  • Possibly because this type of cannibalism Is performed to benefit the current brood
  • There was a nonsignificant tendency for males to avoid tfc when predation threat was high
  • Consumption of a larger clutch was not linked to more elaborate nest construction, suggesting males do not consume eggs for the purpose of nest maintenance
  • Predator presence was linked to large nest entrances among total filial cannibals