Potential nesting sites of Camponotus pennsylvanicus (DeGeer) were investigated in South Carolina to determine if nesting sites features could be characterized by habitat features for black carpenter ant nests. Environmental data from forested plots showed large-scale habitat features such as vegetation density and canopy cover were not useful as indicators for the presence or absence of nests. Small-scale individual nest characteristics such as diameter at breast height of trees, log length, tree defect type or tree species were better indicators of occupied nests. In my study, C. pennsylvanicus preferred mature hardwood (Quercus spp.) trees approximately 30 cm in diameter and pine logs (Pinus spp.) that were approximately 9 m in length. Defects in trees most often associated with nests included tree holes and crotches.
Temperature regulation in nests of C. pennsylvanicus is not well understood. Prior studies reported nest temperature passively reflects ambient temperature during winter months. Because C. pennsylvanicus inhabits wood, it should benefit from the thermal insulating and buffering properties offered by this unique microhabitat.
To evaluate internal compared to ambient temperature in occupied and unoccupied nests, ten C. pennsylvanicus nests were identified in trees on the Clemson University campus. Five of the trees containing C. pennsylvanicus nests were injected with a foam containing the non-repellent insecticide TermidorŽ, containing the active ingredient fipronil, to induce colony mortality. Nest galleries were located using a microwave emitting detector and a digital infrared camera. HOBOŽ H8 Temp / RH / 2x external channel data loggers were used to record ambient and internal nest temperature hourly over 52 wks. Comparison of ambient and internal temperature ranges within nest type were significantly different. Ambient temperature range of occupied and unoccupied nests fluctuated approximately 10°C while internal temperature fluctuation was less, around 2°C. Internal nest temperature of occupied nests mirrored unoccupied nests throughout the year and were not statistically significant. These results indicate that internal nest temperature does not fluctuate over as wide a range as does ambient. According to my results, C. pennsylvanicus is unable to actively regulate its internal nest environment, but can use the insulative properties of trees to dampen wide temperature fluctuations and provide a more stable nest microclimate.
Since C. pennsylvanicus is bound to a central nest, it faces difficulties in foraging that optimize their ability to obtain energy sources. Maximizing net energy yield is one aspect of central-place foraging (CPF) theory. For C. pennsylvanicus to adhere to CPF theory, foragers must structure search patterns to collect food of a high caloric value to compensate for the amount of energy needed to obtain it and return to the colony. This selection for higher energy return should be based on colony nutritional requirements and apparent in both carbohydrate and protein foraging.
To determine if C. pennsylvanicus forages according to CPF theory, carbohydrate and protein solutions were used to ascertain preference at two fixed distances. Additional data were taken to determine if time spent imbibing, varied with concentration, distance or a combination of the two. Solution concentrations of 5 and 30% casein or sucrose were used for the preference and duration studies and were placed at 1 and 15 m distances from the nest. Camponotus pennsylvanicus fed on casein solutions at both distances, with no difference between higher and lower concentrations. However, C. pennsylvanicus selected a higher concentration of sucrose as the distance from a food patch to the nest increased to 15 m. Foragers imbibed sucrose from both concentrations at 1 m with no preference noted between the two solutions. Camponotus pennsylvanicus did not adhere to CPF theory, with respect to protein, but did use a CPF strategy with regard to sucrose selection in this study.
Mean feeding durations indicated that foraging black carpenter ants fed differentially on casein solutions, depending on concentration or distance. Overall casein mean feeding time was significant, suggesting C. pennsylvanicus feeds longer on 30% casein solution regardless of the distance involved. Additional analysis indicated that the effect of distance on feeding duration was only significant at a 5% solution concentration. Overall mean feeding time was significant, suggesting feeding intervals were greater on 30% casein over both distances.