Bios230 – Homework 3

1. You are a conservation biologist and a specialist in amphibians. You are hired by the Mexican government to work on conservation strategies for the Mexican Axolotl (or Ajolte) Salamander, Ambystoma mexicanum. You travel to Lake Xochimilco in Mexico City and capture salamanders by wading into shallow waters and using a net. You mark salamanders with a fluorescent dye and release them. You return one month later and capture salamanders again. You obtain the following data:

Table 1

Year	# Marked and	# Captured	# Marked	Estimated Total
	Released	(July)	(July)	Nx
	(June)
1	60	64	35
2	71	74	31
3	73	79	35
4	70	77	38
5	44	51	33
6	41	47	29

Based on these results, estimate the number of individuals (N_x) in the population for each year (complete the last column of the table). Show your work. Based on your findings, what would you include in your report on the conservation status of the Axolotl at this site?

2. You decide to study the life history of the Axolotl salamander for your PhD at UNAM (National Autonomous University of Mexico). You follow a cohort of salamanders through their lives. During the breeding season of your first year, you collect egg masses from several females and when the eggs hatch, you tag 192 baby salamanders. You release them into a small pond, return every year, capture the marked salamanders, and determine how many are still alive. Based on this, complete the life table below (show your work):

Salamander age (years)	Nx	lx	dx	qx
0	192
1	16
2	13
3	9
4	5
5	2
6	0

3. What type of survivorship curve does this population have? Include a graph of l_x vs age to answer this question (remember to graph l_x on log scale). Explain what this tells us about the life history of the salamanders. What would you recommend to conservation managers in order to help increase the population size of Axolotl in the future? (Answer in 2-3 complete sentences.)

4. Conservation management for Ajolte salamander also includes a captive breeding program, with the goal of eventually releasing salamanders into lakes where they have disappeared. Using artificial ponds, you establish a captive population with an initial size of 98 salamanders. You determine that the females in the population produce an average of 42 surviving young each breeding season. On average, 20 salamanders in the captive population die every year. Based on these numbers, and given unlimited space and resources, how many salamanders would be in your captive population in two years? Ten years? Twenty years? Show all your work.

5. What are the major threats to the Axolotl salamander? This species is remarkable in several ways, including its unusual development (or lack of), its courtship behavior, its use in scientific research, its place in Mexican history and folklore, and traditional medicinal uses. Find and briefly describe something about this species that you find interesting.