EX 2 TECH : Sex and estimating aging

Why is determining an animal’s sex and age important?

Population structure, genetic variation, age/sex ratios, harvest regulations, population trends, source-sink dynamics, behavioral ecology.

How do demographic processes influence behavior?

Behavioral interactions vary by age and sex classes

What makes a good sex/age classification technique?

Works year-round, live/dead animals, multiple body parts, many age categories.

Why can harvest-based sampling be biased?

Changes in movement, habitat use, breeding behavior, and differential harvest susceptibility.

Example of harvest-only data limitation?

Waterfowl Parts Survey → only wing plumage data

Why standardize measurements?

Ensures consistency and comparability.

Common measurement examples by taxa?

All animals: body mass

Bats: forearm length

Herps: snout-vent length

Birds: wing chord/notch

Only truly accurate age method?

Knowing the birthdate.

Why is aging imperfect?

Individual variation, different development rates, genetic factors.

Altricial young?

Born helpless and require parental care. ex: parrot , pelican, songbirds

Precocial young?

Mobile and relatively self-sufficient soon after birth. ex: chicken, duck, rhea

What is egg candling?

Shining light through egg to observe embryo development.

Why do older eggs float more?

Water loss → lower specific gravity → increased buoyancy

Postnatal aging indicators (altricial)?

Growth data (wing, tarsus, weight, feather timing), photo guides.

Postnatal aging indicators (precocial)?

Plumage traits, size vs adults, flight ability.

Molting definition?

shedding and replacing worn feathers

What is a molt limit?

Boundary where two feather generations meet.

What do molt limits indicate?

HY/SY birds; uniform plumage suggests AHY/ASY.

What is skulling?

Assessing skull ossification/pneumatization.

Iris color aging example?

Some species change from gray-brown to reddish-brown with age

Main bird sex determination methods?

Cloacal structures, plumage dimorphism, DNA.

Why is song unreliable alone?

Some females also sing.

Size pattern in passerines vs raptors?

Passerines: males larger (overlap 60–80%).

Raptors: females larger.

What is a brood patch?

Bare skin area on incubating females for heat transfer.

Why is mammal age classification difficult?

Large variation in size, longevity, reproductive timing.

Key mammal aging methods?

Teeth, eye lens dry weight, baculum, body size, growth rings, bones, horns

What is DNAm aging?

Epigenetic clock based on methylation pattern changes.

Baculum aging useful in which animals?

Raccoon, muskrat, mink, weasel, skunk, badger, marten, wolverine (not red fox).

Deer aging indicators?

Body traits, antlers (males), jaw/tooth eruption and wear.

Where is the four-year horn ring usually located in a bighorn sheep?

Near ear line

Mature ram body traits?

Broomed horns, scars, pot belly, swayed back, heavy horn mass.

Why is size unreliable for aging herps?

Influenced by temperature, food, water, density, predation.

What is skeletochronology?

Counting lines of arrested growth (LAGs) in bones.

What study tracks growth/survival over time?

Mark-recapture (CMR)

Male lizard indicators?

Hemipenes bulge, swollen tail base, bright breeding colors.

Age indicator in skinks?

Juveniles often have bright blue tails.

Tail difference between male and female snakes?

Males have longer, thicker tails after vent.

Rough age estimate in rattlesnakes?

Count rattles (very rough)

Plastron shape sex indicator?

Concave = male

Box turtle eye color difference?

Males red/orange; females yellow/brown

Why are shell growth rings unreliable?

Rings can form anytime and wear down

Male frog characteristics?

Smaller, large tympanum, vocal sacs, nuptial pads.

Limitation of frog skeletochronology?

Does not include tadpole stage age.

Size-based sex clue for american alligaor?

>10 ft usually male

What is negligible senescence?

Very old alligators remain healthy/agile with little aging decline