FORAGING DISTANCE IN THE STINGLESS BEE Trigona thoracica

Abstract

The foraging patterns of stingless bees are dependent on resource availability.Human alterations to natural areas will affect the condition of local habitats,and influence the bees' foraging behavior. In this study, we assessed thefamiliarity of Trigona thoracica with two distinct habitats. This studyinvestigates the familiarity of the stingless bee Trigona thoracica with twodistinct habitats. It has the dual purpose of comparing foraging distancebetween the intact forest and disturbed environments, and of evaluating theidea that bees create memory patterns for navigational purposes en route todestinations. We hypothesized that bees forage more frequently in thenatural environment than in the disturbed environment, and are thereforemore familiar with forested terrain. We also suspect that bees are able toform a visual memory in transport, and that they will integrate cues theyacquire in transition to guide themselves home from unfamiliar locations. Weselected a (medium-sized) colony of Trigona thoracica at the base of a Ficusmicrocarpa tree near the entrance to the Khao Chong Peninsular BotanicGardens. The nest was located in a relatively open area, adjacent to twodistinct environments: a densely wooded forest to the east and an altered,semi-natural environment along a highway to the west. One transect line wasplaced in each of these two areas, and three release points along the transectswere determined using GPS (East - Forest area: 350, 650, 1200m; West -Highway: 400, 800, 1200m).

Outgoing bees were collected in plastic bags and tagged with paint markers,Collections ranging in size from sixteen to seventy bees were thentransported in an insect cage to designated release points either on foot or onmotorbike. At each location, two samples (covered and uncovered) werereleased at staggered times. The two transects were completed over thecourse of three days, with a total of twelve releases. On each day we hadsimilar sunny and dry weather conditions. On each day, the nest wasobserved from the first release to at least 1.25 hours after the last release; theactivity of marked bees (entering or exiting the hive) was recorded, as well asthe time of that activity. Percentage returns were calculated for each batch ofmarked bees released from each of the three releasing points on each transect,according to the recorded number of returns for each batch.

There was no significant difference between the number of covered anduncovered bees that returned. This leads us to believe that the bees do notform memory when they are artificially transported, which may be due tofactors, which differ between artificial transport and normal flight behavior.Possible factors include the rate of movement, and the height of travel.Additionally, the mesh-and-plastic carrying cage may have skewed the bee'sexposure to sunlight and added an abnormal level of stress for the bee,altering the bee's ability to assess the solar pattern. These factors wouldcontribute to the bee's incapacity to use egocentric methods for homewardnavigation. We found that the bees are more familiar with the natural habitatthan the disturbed habitat. The forage distance was determined to be 3.676km in the forested area and 1.973 km along the highway.