BIO 262 Mating + Rarity, Spacing, and Territorality

Monogamy

pair bond between a male and female

Polygyny

1 male, several females.

Polyandry

1 female, several males.

Simultaneous

multiple pair bonds occur at the same time

Simultaneous polygyny

1 male with 2 or more females at the same time

Simultaneous polyandry

1 female with 2 or more males at the same time

Sequential

multiple pair bonds occur over a single breeding season

Sequential polygyny

1 male with 2 or more females but only one at a time

Sequential polyandry

1 female with 2 or more males but only one at a time

Female

sex with the larger gametes, who cares for the developing zygote (sometimes within themselves). Greater ♀ 'investment' in offspring means that this sex generally has fewer offspring and thus pays more attention to offspring quality.

As sexual dimorphism ________, males more able to 'defend' multiple females and probability of polygyny _________

increases

Polygny threshold

territory quality varies so much that it is better for a female to mate with an already-mated male on a 'good' territory than to mate with a monogamous male on a 'bad' territory

When offspring require both parent's attention, __________ may be favored

monogamy

Passerine birds

A. Extensive parental care; 95% of 261 North American passerines are ____________

B. __________ occurs in productive and patchy environments (i.e., areas with very good and very bad places for feeding young

monogamous, Polygyny

Red-winged blackbird: __________ passerine that occurs in marshes, patchy environments where some areas are much better than others in terms of food production.

a. Males that possess extremely productive territories maintain harems.

b. Territories with ________ Females are rich in food --> Males with larger harems produce more young per Female:

c. Territories with single Females are disproportionately low in food and produce fewer young per Female.

d. As a result, polygyny benefits both Males and Females.

polygynous, multiple

'Imperfect' monogamy in Seychelles warblers:

- Males spend ______ time guarding female and ______ time foraging as the number of neighboring males increases.If they don't guard the female, though, neighboring males sneak in and impregnate the female (leaving the cuckolded male to raise someone else's offspring)

more, less

Monogamy isn't perfect: _______-pair paternity (father raising some offspring belonging to other ♂s) is surprisingly common

extra

Extra pair paternity examples

- Moller

- Blue tit

- English Sparrow

Lizards: no parental care, so _________ is extremely common

polygyny

Females have mammary glands; asymmetrical investment in offspring predisposes Females towards more parental care and favors _________ but can lead to ___________

monogamy, polygyny

Mammals: Greater Male:Female body size ratio correlated with higher likelihood of __________

polygyny

Polyandry examples

- Tinamau

- Tasmanian hen

If you're not winning, change the game (♂s of same species may adopt different mating strategies)

A. Temporary phenotypic shifts (Hanlon et al 2005):

B. ______ (a kind of snipe):

I. Lekking Male

II. Satellite Male

C. Sunfish: territorial and non-territorial Males

I. Territorial Male

II. Non-territorial Male

D. ________ beetles

I. Horned Males

II. Hornless Males

Ruff, Dung

Temporary phenotypic shifts (Hanlon et al 2005)

small Australian cuttlefish pretend to be females until they're large enough to compete with bigger males.

Ruff (a kind of snipe): 2 distinct kinds of Males

I. Lekking Male -

II. Satellite Male -

I. tries to attract ♀s by displaying

II. sneaks copulations at edge of lek

Sunfish: territorial and non-territorial Males

I. Territorial Male -

II. Non-territorial Male -

I. maintains territory where Female deposits eggs

II. looks like Female, sneaks in when territorial Male isn't looking to fertilize some eggs (thus reproducing without having to defend territory)

Dung beetles

I. Horned Males -

II. Hornless Males -

I. larger, guard brood burrow, mate with Females

II. smaller, better eyesight, digs alternate burrow that intersects guarded burrow and surreptitiously inseminates some eggs.

Ultimate mating strategy:

sex change! (same individual is both Male and Female)

Ultimate mating strategy examples

- Hogfishes (Hoffman):

- Crepidula molluscs

3 things that determine rarity

1. Geographic range

2. Habitat tolerance

3. Local Population size

Geographic range

extensive or restricted

Habitat tolerance

broad (can live in many habitats) or narrow (few habitats they can survive in)

Local population size - small or large

small or large

How are sessile organisms dispersed in space?

A. Random

B. Clumped

C. Uniform

I. Poison

- Sagebrush

- Sessile marine organisms (sponges, coelenterates)

How can we characterize space use in mobile organisms?

A. Single individual

I. Home range (area)

II. Minimum convex polygon method

B. Territory

I. Behavioral

II. Ecological

III. Territorial species have individuals spaced out over environment

a. Center of gravity method:

Home range (area)

area that is "normally" frequented by the animal

Minimum convex polygon method

a. Smallest area that encloses all points or has points on boundaries

b. No inner angle greater than 180°

Territory

I. Behavioral:

a defended area

Territory

II. Ecological:

an exclusive area (i.e., no other animal or group occurs there)

Territory

III. Territorial species have individuals spaced out over environment

a. Center of gravity method:

Take home range and compute average X andY coordinates in space; if home ranges are on average spaced out, they are overdispersed and probably territorial.

What broadly determines territory size?

A. Balance between benefits and cost:

I. Benefits first increase, then level out as territory size increases because you 'max out' the resources you can utilize.

B. What if territories improve (or resources get more abundant, risk of predation decreases, etc.)? Territory size should decrease

C. What if competitors become more numerous? Territory size should also decrease!

What specifically determines territory size?

A. Avoidance of predation: animals defend territories because those with territories are less vulnerable to predators.

B. Increase or facilitate mating opportunities

C. Competition for other limiting resources

D. Increased food supply

Two expectations about food supply and territoriality

1. As the organism's food requirement (i.e., metabolic rate) increases, territory sizes should increase.

2. As food density increases, territory size should decrease

Evidence that increased food supply motivates territoriality

Between-species (interspecific) evidence: organism weight versus territory size (Haskell et al 2002)

I. Larger organisms have larger territories.

II. Predators have larger territories than herbivores of same weight (perhaps because predator food is "rarer" than herbivore food; supports prediction #2)

III. Slope of herbivore line is ~0.75. Supports prediction #1, since territory size increases relative to body size at same rate as does metabolic rate.

IV. Slope of predator line is ~1.3. Rejects prediction #1, since territory size increases disproportionately with body size. Why?

a. Larger predators like hawks have less dense food than do sparrows; makes predator slope >> 0.75.

V. Kelt and Van Buren: Mammal home ranges exhibit same relative relationships, but y-intercept of both predator and herbivore lines were higher than that for birds.

Evidence that increased food supply motivates territoriality

Within-species (intraspecific) evidence

I. Snowy owl and lemmings (Pitelka): Territory size of snowy owls inversely correlated with lemming density.

II. Nuthatches (Enokkson and Nilsson): Both observational and experimental work show that territory size decreases as food density increases

III. Fence lizards, Sceloporus sp. (Simon): Both Male and Female defend territories (males are larger and have larger territories). For both Male and Female, territory size inversely correlated with food density. When food density increased by adding mealworms, territory size decreased. When food addition stopped, territory size increased

Other adaptive rationales for territoriality

A. Australian magpies

B. Dragonfly territories

C. Jamican brown lizard