L3 Vital Statistics: pop ecology basics

Question 1

what is an advantage of stats in conservation?

Answer 1

we can calculate population numbers and this allows us to calculate recruitment success or failure. We can use this info to inform future decisions.

Question 2

what do the letters indicate?

Nt+1 = Nt + B + I - D - E

Answer 2

Nt = current population size 
Nt+1 = population size of next generation
B = Birth rate
I = Immigration rate
D = Death rate
E = Emigration rate

Question 3

what are the basic vital rates to calculate for a pop? (4)

Answer 3

Birth, death, immigration, emigration

Question 4

What are other pop factors that are good to calculate other than the basic vital rates? (2)

Answer 4

• sex ratio

- density

Question 5

why should we calculate pop abundance as conservationists?

Answer 5

1) determine if a pop declining or growing
2) calculate effects of predation
3) calculate the effects of introducing a biological control agent
4) calculate no. of individuals we can harvest

Question 6

what is the calculation for abundance?

Answer 6

abundance = count / probability of detection

Question 7

what is a ‘census’ count?

Answer 7

when you are certain you have counted all individuals of a pop without using stat techniques

Question 8

give examples of counting abundance that without an estimate is not a census (3)

Answer 8

bird-call counts
counting burrows
mammal capture in traps

Question 9

why would we use estimates rather than census?

Answer 9

difficulty & money

Question 10

What are the two methods to estimate population abundance?

Answer 10

1) Lincoln-Peterson method i.e. capture mark recapture (CMR)

2) Distance sampling

Question 11

basic method for lincoln-peterson method?

Answer 11

count the first sample, mark them, let them go & take a second sample count how many are and aren’t marked.

Question 12

the calculation for lincoln peterson method is this:
abundance = n1/ (m2/n2) 
OR
abundance = n1*n2/m2
what are the letters?

Answer 12

n1 = no. individuals in first sample 
n2 = no. individuals in second sample 
m2 = no. individuals marked in the second sample

Question 13

what are the assumptions of the lincoln-peterson CMR method? (3)

Answer 13

1) During the time the population is closed (no im or em)
2) marking individuals doesn’t increase death rate
3) all individuals are equally likely to be caught

Question 14

basic method for distance sampling?

Answer 14

walk along a transect and estimate the distance of the individuals you see/count. OR stand still and estimate distance e.g. bird calls.
Present data in a histogram using probability vs distance (x axis)

Question 15

what are the assumptions for distance sampling?

Answer 15

1) Assumes if there is 0mm distance from you and an individual you would definitely see it.
2) The probability of seeing an individual decreases with distance

Question 16

what is the equation for distance sampling?

Answer 16

abundance = area under curve / total rectangle

Question 17

why is measuring survival more complicated and how do you measure it?

Answer 17

• more complicated because it’s an open pop - can die or em

- you can measure by using CMR and calculating how many marked individuals make it from one time period to the next.

Question 18

when calculating survival what do these mean?

φt, pt

Answer 18

φt = prob that animal alive at time t survives to time t+1 (another generation)
pt = prob that animal alive at time t is captured at time t

Question 19

What basic factors do we measure for in reproduction? (6)

Answer 19

1) maternity
2) paternity
3) litter size / clutch
4) fecundity - average no. of offspring per individual of a given age in a given time (generation)
5) recruitment - net population production after births and deaths are accounted for
6) fecundity X survival - av reproductive contribution after birth and death accounted for

Question 20

what is sex ratio? what types are there?

Answer 20

ratio of female:male or percents
head - count sex ratio e.g. 1:1
breeding sex ratio e.g. (in a harem) 1:20

Question 21

what do conservationists need to be careful of when maintaining sex ratio?

Answer 21

needs to be natural e.g. when raising turtles - be aware that gender is temperature dependent in eggs

Question 22

suggest a method to estimate sex ratio

Answer 22

poo

or extract dna from fresh faecal samples (if you want to be posh)

Question 23

which case study was used in this lecture and what was the outcome?

What is a case study weighing out the importance of differing conservation strategies in relation to population growth rate?

Answer 23

The black bear (Ursus americanus). results showed that lamda was most strongly influenced by recruitment (net pop production after births & deaths), meaning recruitment is the biggest factor to increase the pop but only in human-protected populations. Whereas unprotected populations are more affected by adult survival (more offspring in adults) (Mitchell et al., 2009)

Question 24

what does lamda show?

Answer 24

tells you whether to focus on improving survival rates in adults or reproduction rates to conserve / increase the population.

Question 25

woodlouse capture mark recapture 
N1 = 56
N2 = 49
M2 = 27 
what is the estimated abundance?
abundance = n1/ (m2/n2) 
OR
abundance = n1*n2/m2

Answer 25

56 * 49
———— = 102 abundance
27