Sunday crab lab Wear warm clothes bring gloves
Sunday crab lab! Wear: warm clothes, bring gloves and RUBBER BOOTS. If raining, bring umbrella. Transport on Sunday: Either arrive before 12 noon at Spanish Banks, or 11: 50 latest in Zoology courtyard. Monday: meet in Zoology courtyard at 1 pm
Snow Goose La Pérouse Bay
Herding flightless geese into a “keyhole” net
Recording which birds are marked, and marking new birds
Goose biologist Goose leg bands
Year LPB Colony size
Mark recapture lectures • • Petersen method Closed population Schnabel method Schumacher-Eschmeyer Open population Jolly Seber Overview of methods to help your reading of Krebs Chp 2
Closed populations No individuals enter or leave the population between surveys Survey 1 Survey 2
Open populations Individuals enter or leave the population between surveys Survey 1 Survey 2
What makes a population closed? • Dispersal barriers • Philopatry • Large surveyed area • Slow reproductive/death rate • Short time between surveys
What type of population are the snow geese?
Petersen method: Closed population Survey 1: Catch several animals Mark all M animals Return animals to population Survey 2: Catch C animals Count recaptures (R) Return animals to population
Survey 1: M = 12 Survey 2: C = 15 R=4
What is the total population size (N)? Note that the proportion marked in the population equals the proportion marked in the 2 nd sample M =R N C M = 12 N =MC R C = 15 R=4
What is the total population size (N)? Note that the proportion marked in the population equals the proportion marked in the 2 nd sample N = 13 * 16 5 M = 12 -1 N = (M+1) (C+1) -1 (R+1) C = 15 R=4
When would Petersen give you a bad estimate? • Population not closed • Marked animals likely to be re-trapped • Marked animals likely to die • Marks fall off
Schnabel method: closed population Survey 1 Survey 2 Survey 3 Survey 4 Survey 5 Essentially, Petersen estimates on multiple surveys
Schnabel method: closed population Survey t: Catch Ct animals Record Rt recaptures Mark Ut unmarked animals Return animals to population
Schnabel method: closed population Survey t: Catch Ct animals Record Rt recaptures What’s the relationship between Ct, Rt, and Ut ? Mark Ut unmarked animals Ct = Rt + Ut Return animals to population
Schnabel method: example Time (t) Ct Rt 1 20 2 20 3 20 4 20 Ut 5 13 10 How many individuals marked by beginning of time 5?
Schnabel method: example Time (t) Ct Rt Ut 1 20 0 20 2 20 5 15 3 20 7 13 4 20 10 10 How many individuals marked by beginning of time 5?
Schnabel method: example Time (t) Ct Rt Ut 1 20 0 20 2 20 5 15 3 20 7 13 4 20 10 10 Σ = 58
Schnabel method: example Time (t) Ct 1 Rt 20 In general: + U 2. . Ut-1 2 Mt = U 1 20 Ut 0 20 5 15 3 20 7 13 4 20 10 10 Σ = 58
Schnabel formulas: N = Σ (Ct Mt) Σ Rt+1 Marked > 10% of population Marked < 10% of population ( just weighted average of Petersen estimates!)
Schnabel method: example Time Ct (t) 1 20 Rt Ut Mt 0 20 0 2 20 5 15 20 3 20 7 13 35 4 20 10 10 48 C t. M t
Schnabel method: example Time Ct (t) 1 20 Rt Ut Mt C t. M t 0 20 0 0 2 20 5 15 20 400 3 20 7 13 35 700 4 20 10 10 48 960 Σ = 22 Σ = 2060
Schnabel method: example Time Ct (t) 1 20 Rt Ut 0 Mt 20 0 Σ (Ct M 94 2 N =20 5 t) = 2060 15 =20 3 20 4 20 Σ Rt 22 C t. M t 0 400 7 13 35 700 10 10 48 960 Σ = 22 Σ = 2060
Schnabel method: example Time Ct Rt Ut Mt C t. M t (t) 1 20 0 0 What proportion of total 2 20 5 marked 15 by 20 population end? 400 3 20 7 13 35 700 4 20 10 10 48 960 Σ = 22 Σ = 2060
Scumacher-Eschmeyer method (for Schnabel experiment) N=CM R R=1 *M C N y = mx + b
Scumacher-Eschmeyer method (for Schnabel experiment) R=1 *M C N N=CM R R C Slope = ? M
- Slides: 30