Home Search for: Advanced Search Foraging Habits of Seed Harvesting Ants Submitted by: Peter Nonacs Area(s) of application: Biology Statistical method(s): Anova - Linear Regression - Residuals Analysis - T Test Filename: seed_ant.txt Keywords: ants, forage, categorical, numerical, observational, Sierra Nevada Aquatic Reserach Laboratory Source: Dataset entered on: 2005-08-23 User rating (5 = best): Be the first to rate this dataset! Download Dataset Summary The data for both files was collected at the Sierra Nevada Aquatic Research Laboratory (SNARL) in the Great Basin Desert Province. Collection trays were placed into the ground at different distances from the entrance to the ant colonies' mounds, and any ants walking into them were trapped. Thus the data may be considered as random samples of ants at various distances. Documentation ================================ GENERAL EXPLANATION OF THE STUDY ================================ The two accompanying data files are from a study on the foraging habits of two species of ants: thatch ants (Formica planipilis) and seed harvester ants (Pogonomyrmex salinus). The study was concerned with the ant colonies' different "strategies" for optimizing the balance between collecting food and exposure to risk. The idea, in its simplest form, is that sending more ants to look for food farther away from the colony is more likely to increase the colony's food supply; traveling away from the colony, however, exposes ants to the risk of death by starvation and predation. Natural selection suggests that colonies will develop foraging strategies that maximize the colony's net gain, defined as how much the colony grows--this depends primarily on its food supply--minus how many ants die. A variety of different maximizing strategies exist, and different species often have different strategies. Some colonies develop "worker-conservative" foraging strategies, in which ants foraging at greater distances consume relatively more food: this minimizes the risk of starvation and leads to fewer deaths. Other colonies use strategies that conserve energy (the colonies overall supply of food). In this case long distance foragers, who are more likely to die, will consume less food so that their deaths will not be as much of a strain on the colony's food supply. More specifically, this study investigated the relationship between the size of the ants and the distance at which they foraged. Other studies have shown that larger ants use energy more efficiently than smaller ones, and this suggests that larger ants would be more likely to forage at greater distances. Thus ants were collected at various distances from the colony, weighed, and measured. Because an ant's weight provides a measure of how much food, or energy, it carries, and because headwidth measurements allow the ants to be classified by size, the data provides detailed information on the correlations among ant size, foraging distance, and energy supply. This information, in turn, gives insight into foraging strategies: we can, for example, determine whether a colony's strategy is "worker-conservative" or "energy-conservative," or a more complex combination of the two. We might find, for example--by analyzing the relationships among size, foraging distance, and energy supply both for the colony as a whole and within the separate size classes--that a colony's overall strategy is "worker-conservative," but that within size classes the strategy is "energy-conservative." These analyses, finally, illuminate the colony's survival strategies and provide evidence for or against competing evolutionary theories. This study has not yet been published (11/29/99). ============================= BRIEF DESCRIPTION OF THE DATA ============================= The data for both files was collected at the Sierra Nevada Aquatic Research Laboratory (SNARL) in the Great Basin Desert Province. Collection trays were placed into the ground at different distances from the entrance to the ant colonies' mounds, and any ants walking into them were trapped. Thus the data may be considered as random samples of ants at various distances. The data on the thatch ants contains a total of 1199 samples, taken from a total of 11 different colonies. The data on the seed harvester ants contains a total of 577 samples, taken from 8 different colonies. ========================= HOW TO USE THE DATA FILES ========================= The actual data files are comma delimited text files. The first rows contain the abbreviations for the information recorded for each sample. The remaining rows each represent a single ant's corresponding information. There are five variables in both files. The variables are the same in both files, although the values they may assume are not always the same. Here is a brief explanation of each one: COLONY: ............This is a number or letter that identifies which colony the sample was taken from. It is important only for distinguishing between ants from the same colony and ants from different colonies. DISTANCE: ..........Tells how far from the mound's entrance the sample was taken. Given in meters. MASS or WT. (MG): ..How much the sample weighed in milligrams. This variable is used as a measure of how much food (energy) each sample had. HEADWIDTH: .........A measure of the sample's maximum headwidth. The units here are basically arbitrary, and correspond to ruled increments that can be seen in the microscope with which the sample is measured. Headwidth is a good indicator of an ant's size, and can be used to classify the ants by size. HEADWIDTH (MM): ....Same as "headwidth," only given in millimeters. WORKER CLASS: ......A size classification. In the thatch ant data there are five possible classes: "<30", "30-34", "35-39", "40-43", and ">43". In the seed harvester data there are four size classes: "<37", "37-38", "39-40", and ">40". Download Dataset