Content provided in partnership with
Antlion Foraging: Tracking Prey Across Space And Time
Ecology, Oct, 1999 by Philip H. Crowley, Mary C. Linton
RESULTS
Table 1 summarizes the outcome of the simulation analysis, with costs of movement set to the estimated values. Because the outcomes for within-site transects were very similar, these are not shown. The highest gain strategy overall featured a relatively long interval of 35 d, but with substantial discounting of preceeding data (weighting = 0.7) that implied a window of 3.33 d (Eq. 2); a relocation threshold at 1.17 mg/d, half of the grand-mean gain rate; and the minimal displacement of one 0.5-m step. A similar pattern is derived from the median values for each component from the top 32 strategies, representing those with gain rates within 1% of the highest rate: an interval of 45 d and weighting of 0.9 (i.e., a window of 10 d), threshold of 1.17 mg/d, and displacement of three 0.5-m steps.
- Most Popular Articles in News
- The Ten Best Laptop bags
- Tata plans cheapest-ever car for Indian market
- GLOBALIZATION AND THE DEVELOPMENT OF UNDERDEVELOPMENT OF THE THIRD WORLD
- Corn is good for you; Corn is not only a tasty treat, but also a cereal that ...
- THE 50 BEST STYLISH HANDBAGS TO CARRY
- More »
Because the analysis of Linton (1995) indicated that scales of spatial and temporal autocorrelation are small (i.e., at or below the scales of spatial and temporal resolution in the data) for the SBD-NL transects, we can compare the previously discussed patterns with those expected according to the upper-left box of Fig. 1. We note that optimal displacements are small and assessment periods are relatively long, as expected. Moreover, a threshold of 1.17 mg/d (i.e., half of the overall mean) can be considered a fairly high value, in light of the substantial variability in the data and the relatively short window. In other words, the site assessment value needs only to fall below half of the overall mean value during a relatively brief assessment period to trigger relocation, not a particularly stringent requirement. Thus, these results seem generally consistent with the scheme in Fig. 1, although this in no way constitutes a rigorous test of these predictions (see Discussion).
The highest gain rate of 2.445 mg/d was achieved with a mean pit relocation frequency of 1.65 over the 60-d observation period and a total movement distance [TABULAR DATA FOR TABLE 2 OMITTED] of 0.5 m, generally consistent with the low relocation frequencies and short movement distances in field observations (Linton 1995). However, antlions that never relocated were able to do almost as well, achieving a highest gain rate of 2.388 mg/d, 97.7% of the gain achieved by those following the top strategy of occasional relocation. Particularly when relocation is energetically costly, a strategy of not relocating at all can apparently do nearly as well as a more complex, conditional relocation strategy.
In fact, the gain surface formed above orthogonal axes based on most pairs of the four strategy components is relatively flat [ILLUSTRATION FOR FIGURE 3 OMITTED], especially along weighting and threshold axes (e.g., [ILLUSTRATION FOR FIGURE 3D OMITTED]). Over all sites, years, and transects, 60% of all strategies investigated generated gain rates within 8% of the highest rate, and 90% generated gain rates within 18% of the highest. The results, however, are somewhat more sensitive to interval and displacement; in particular, short intervals and large displacements clearly result in too much energetically expensive pit relocation [ILLUSTRATION FOR FIGURE 3C OMITTED].
Find Research Guides for:
Find Featured Titles for: Reference
- Academe
- African American Review
- African Arts
- African Studies Review
- Afro-Americans in New York Life and History
- Alabama Heritage
- Alabama Review
- American Mathematical Monthly, The
- Anglican Theological Review
- Annals of Dyslexia
- Arab Studies Quarterly (ASQ)
- Auk, The
- Australian Journal of Anthropology, The
- Christian Century
- Natural History