Jolly-Saber Method Case Study

Based on the Jolly-Saber method the population size was estimated at 31 individuals for the Glyn Taff site which was derived from the data collected in table 1.
The Jolly-Saber method assumes that the small mammal population is open both geographically and demographically as well as more than two capture sessions taking place. This assumes that migration can occur within the population and new members of the population can be born. Table 2 shows the figures used to determine how the Jolly-Saber estimate was determined followed by the mathematical equations used.
Sabers estimate was also used to determine confidence intervals but the figure used cannot be assumed to be an accurate estimate for population size as it only used two of the three
The data gathered suggests that this did not occur as the animals appeared to be in little distress and no deaths occurred from handling any of the animals. The opposite may be applicable in this case where animals may become “trap happy” and return to the trans as they offer shelter and food. The data in table 1 shows six individuals out of seventeen new animals returned to the traps on three separate occasions as well as one returning once. This could be indicative of trap happiness as a high proportion of the total caught population returned once or more. As the traps were provisioned after each trapping session coupled with good handling practice may encourage individuals to return to the traps. Table 3 shows which traps caught the same individual on multiple occasions and the distances travelled between them. This clearly shows that individual animals did not travel far from the location of their first trapping which could indicate them favouring that area due to “trap happiness” but is more likely due to the fact that they do not travel large distances and generally remain within a certain
Figure 5 shows an arial image of the site perimeter and it should be noted that the vast majority of the site is grassland with tree and uncut vegetation bordering the site. Figure 6 shows the density of animals caught in traps in each area of the site. It clearly displays a strong catch rate in groups C, D and E with no animals being caught in groups A and B during the entire trapping exercise. This trend may be due to groups D and E being located next to a woodland and group C next to an uncut heavily vegetated area. Although group B is located close to group C, it also extends down next to an urban development which may deter animals from occupying this area. This may have a consequence on the estimation of abundance as much of the site does not suit the habitat of small mammals. If two studies were undertaken for the two sides of the site a more accurate abundance may be determined for the site. The final method of population estimation for the site is the use of a cumulative frequency graph. Graph 1 shows the cumulative frequency of the data gathered and the line intersecting at a proportion of 1 indicates an estimated population. The graph shows an estimated population of 42 individuals which is slightly higher than the Jolly-Saber method but still within a feasible number for the population of the