REPORT 2 Estimating the population size of mobile organisms – Mark Recapture methods There are two parts to this practical. In the first (PART ONE), you will monitor the movement patterns of cars (bats) into and out of UWC campus through the main gate on a given working day. This information provides background data on the “biology” of cars (bats) at UWC. You will then implement a detailed mark-recapture study of the cars (bats) (PART TWO).

PART ONE – A preliminary study of the movement patterns of cars into and out of UWC on a working day. Aims to summarise the movement patterns of cars (bats) into and out of UWC during a normal working day, in order to provide background information on the “biology” of cars (bats) at UWC Methods Students must sort themselves into groups of two. Each group will count the number of cars entering (IN) and leaving (OUT) UWC through the main gate, over a 60 minute period, from 07h00 – 20h00, on a selected working day. Cars will be counted in 10 minute intervals and data will be entered into the appropriate space on the attached Table template (Table 1). It is suggested that the earlier and later time slots be taken by groups of students that live close to the UWC campus. Raw data must be entered into a spreadsheet within 24 hours of collection, and 30-minute running means need to be calculated: spreadsheets should be forwarded to the course coordinator immediately thereafter for compilation and distribution to the remainder of the class.

The types of output shown in Figure 1 can then be generated: The upper panel in Figure 1 shows the numbers of cars coming IN to (blue) and OUT of (red) UWC’s main gate at ten-minute intervals over a working day during September 2005: Note the high level of “noise” in the data. The lower panel in Figure 1 is a line graph of the 30-minute running mean, calculated at ten minute intervals from the above data – colour codes as in the original: Note that patterns of movement are much clearer. What can you say about the “biology” of cars at UWC on this date? What hypothesis can you propose to account for your observation? How would (NOT WILL) you set out to test your hypothesis?

PART TWO – Estimating the car (bat) population size at UWC campus Aims Using appropriate mark-recapture methods, to estimate the car (bat) population size at UWC during a working, and to determine the 95% confidence intervals around this estimate/s to prepare a full scientific report that summarises the statistical methods used and the results obtained, and which interprets the results as if the cars were actually bats (see below) Methods Students will work in groups of four. Each group of students will go to the main gate of the UWC campus at a time and date to be decided upon by the class - that decision to be informed by the strictures imposed by the mathematical models used to estimate population size. The group will make a note of the car registration numbers of ALL cars entering OR leaving UWC through the main gate over a 30 minute time period. Data MUST be entered onto an Excel spreadsheet and sent to the course coordinator for compilation and distribution to the remainder of the class within 24 hours of collection. When entering data there MUST be no spaces between the numbers and letters of number plates (e.g. WHIZZO1WP, CA266534): all data must be entered in UPPERCASE

The number plates represent individual specific markings and can be used to track the movement of individual cars. From the collected data, you will estimate the bat population size (with 95% confidence intervals) following the methods outlined in Chapter 2 of Krebs (1999). When analyzing and interpreting your data you must take the following into consideration: Do you violate any of the assumptions of the mathematical methods? If so, which ones? How does your violation of the assumptions of the method influence your interpretation of the data? What other assumptions are you making in your methods?

Your report must be written as if the cars counted were actually bats – the UWC campus being a cave, and main gate being the cave entrance: bats leaving at sunset and arriving at dawn. This means that your introduction should focus on bats, your materials and methods should include a section of how you caught and marked the bats, and you obviously need to discuss your findings in the context of the bat literature (especially population sizes). I do not want to see the word car mentioned anywhere in the text of your report! RUBRIC