Monday, January 25, 2016

Behavioral analysis of Madagascar Hissing Cockroaches





Methods

                In our study of these insects, our procedure consisted of timed periods of study. Specimens were placed in a clear plastic container with pieces of graph paper as the substrate at the bottom, allowing hiding, but providing a clear contrast to the dark-colored specimens. At intervals throughout the study period, modifications were made, such as the addition of food or a hide to the tank, the turning off of a overhead light, and the addition of a second specimen. After the study period ended, a seperate specimen was examined in various behaviors, such as reaction to being flipped over or having air blown onto them. This period was not timed, but instead ended when all possible procedures had been performed upon specimens.

Results

                During examination period, the main observations involved three basic behaviors, namely moving across the tank, staying in one place, or twitching the antennae. Other behaviors were documented as slight modifications on these three, documenting how antennae were being twitched or the speed that the cockroach was moving at.

                When cockroaches were handled, brushed, or otherwise touched or disturbed, unless the interaction was a slight brush on the middle of the back, the roaches reacted strongly, usually either hissing or dodging away or towards the disturbance. From these observations in captivity, I predict that in the wild, these insects have many predators and use these methods of avoidance to keep themselves alive.

                When new hide objects were added or the substrate was moved, the roaches would often either avoid the new or moved object or hide underneath it. This shows that these insects may prefer to be underneath leaves or rotting logs in their native habitat, slowly devouring the decomposing plant.

                In righting and avoidance behaviors, the responses differed noticeably in the reaction. Avoidance behavior seemed to take longer to react and was much less sudden. However, when the roaches were flipped over, all quickly would right themselves via bending their bodies up and to the side, forcing their weight towards the ground in the proper orientation.

                The cerci were observed to produce the distinctive hissing sound when the cockroach was disturbed. I am not entirely sure why the cerci produce this sound, but my particular theory is that, by producing the sound from the cerci, a cockroach may be able to convince a predator that its tail is a false head, letting the creature lunge for the tail, but not killing the roach. This behavior is common in reptiles and winged insects, but until now, I had not observed it in a roach or termite. This shows that optimal behaviors for survival are almost universal, regardless of the animal that is carrying them out.

                The timed study period is documented in the table on the next page, as is graphical analysis of the amounts of time spent doing the three most common behaviors.








                The graph above displays the number of minutes the roaches spent doing each of the three most common actions. The precise values are 7 minutes for sitting or otherwise not moving, 5 minutes and 40 seconds for crawling or otherwise moving around the tank using the legs, and 19 minutes (the entire period) for twitching antennae. This value may seem surprising for twitching antennae, but at least one of the roaches studied, even while sitting or crawling, was twitching their antennae throughout the entire period.


Time
Behavior
Notes
0:10
going underneath paper bedding

0:20
sitting

0:30
twitching antennae

0:40
crawling

0:50
twitching antennae

1:00
quickly crawling

1:10
exploring other side of tank

1:20
sitting

1:30
moving mouthparts

1:40
crawling

1:50
moving to other side of tank

2:00
no change

2:10
twitching antennae

2:20
crawling

3:00
twitching antennae

3:30
cleaning antennae?
moving antennae down and touching with mouthparts. behavior unknown.
4:40
sitting

5:00
no change
cardboard added, tube in middle of tank
5:10
twitching antennae slightly

5:20
antennae stopped twitching

6:00
asleep?
has not moved for some time in any way
6:30
twitching antennae slightly

6:40
sitting

6:50
sitting

7:00
twitching antennae

7:10
antennae stopped twitching

7:40
twitching antennae

8:00
no change
food added, piece of banana
8:30
sitting

9:00
twitching antennae slightly

9:15
moving mouthparts

10:00
no change
added second roach, known as Small. Previous roach Big.
10:10
Small and Big interacting, touching mouthparts
smelling or feeling?
10:30
Small hiding underneath Big

10:40
Big antennae twitching

11:00
Small still hiding under Big

12:00
no change

13:00
no change

14:00
no change

15:00
no change until Small handled to be removed, then hissed

15:00
Small removed, light added

15:00
climbing away from light

15:30
walking around side of tank, away from light

16:00
moving more slowly

16:30
moved into middle of tank, stopped hugging wall

16:50
crawling

17:00
no light, crawling

17:45
hugging wall

18:00
climbing wall

18:30
sitting, antennae twitching

19:00
cleaning antennae


1 comment:

  1. Impressive observations! I can't wait to read more of your experiments.

    ReplyDelete