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 1pm

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

LPB Colony size Year

Mark recapture lectures Petersen method Schnabel method Schumacher-Eschmeyer Jolly Seber Closed population Open population 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

Individuals enter or leave the population between surveys 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: Survey 2: Catch several animals Catch C animals Count recaptures (R) Mark all M animals Return animals to population Return animals to population

Survey 2: C = 15 R = 4 Survey 1: M = 12

What is the total population size (N)? Note that the proportion marked in the population equals the proportion marked in the 2nd sample M = R N C N = M C R M = 12 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 2nd sample N = 13 * 16 5 -1 N = (M+1) (C+1) (R+1) -1 M = 12 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 Catch Ct animals Survey t: Mark Ut unmarked animals Return animals to population Record Rt recaptures

Schnabel method: closed population Survey t: Catch Ct animals What’s the relationship between Ct, Rt, and Ut ? Record Rt recaptures Mark Ut unmarked animals Ct = Rt + Ut Return animals to population

Schnabel method: example Time (t) Ct Rt Ut 1 20 2 5 3 13 4 10 How many individuals marked by beginning of time 5?

Schnabel method: example Time (t) Ct Rt Ut 1 20 2 5 15 3 7 13 4 10 How many individuals marked by beginning of time 5?

Schnabel method: example Time (t) Ct Rt Ut 1 20 2 5 15 3 7 13 4 10 Σ = 58

Schnabel method: example Time (t) Ct Rt Ut 1 20 2 5 15 3 7 13 4 10 In general: Mt = U1 + U2..Ut-1 Σ = 58

Schnabel formulas: N = Σ (Ct Mt) Σ Rt N = Σ (Ct Mt) Σ Rt+1 Marked > 10% of population N = Σ (Ct Mt) Σ Rt+1 Marked < 10% of population ( just weighted average of Petersen estimates!)

Schnabel method: example Time (t) Ct Rt Ut Mt CtMt 1 20 2 5 15 3 7 13 35 4 10 48

Schnabel method: example Time (t) Ct Rt Ut Mt CtMt 1 20 2 5 15 400 3 7 13 35 700 4 10 960 48 Σ = 22 Σ = 2060

Schnabel method: example Time (t) Ct Rt Ut Mt CtMt 1 20 2 5 15 400 3 7 13 35 700 4 10 960 N = Σ (Ct Mt) = 2060 = 94 Σ Rt 22 48 Σ = 22 Σ = 2060

Schnabel method: example Time (t) Ct Rt Ut Mt CtMt 1 20 2 5 15 400 3 7 13 35 700 4 10 960 What proportion of total population marked by end? 48 Σ = 22 Σ = 2060

Scumacher-Eschmeyer method (for Schnabel experiment) N = C M R R = 1 * M C N y = mx + b

Scumacher-Eschmeyer method (for Schnabel experiment) N = C M R R = 1 * M C N R C Slope = ? M