Mammalogy - Exam 2

what are the two suborders or primates & how did they migrate

what are the two suborders or primates & how did they migratewhat are the two suborders or primates & how did they migrate

Stepsirrhini: lemurs, aye-aye, & relatives

∙ mainly in Madagascar, Africa, SE Asia

∙ presence of tooth comb - lower incisors & canine teeth all look the same to help with grooming

Haplorrhini:  monkeys, apes, us, & more

∙ Americas, Asia, Africa

∙ no tooth comb

hypothesis for how the eastern hemisphere primates came to be is how they likely rafted on big islands & with favorable water currents they end up traversing from eastern hem to western hem

what are primate color vision

they have components in eyes where they can see in low lights → they are not nocturnal, but crepuscular

why are rodents so successful & the most diverse group of living mammals

why are rodents so successful & the most diverse group of living mammals

rapid reproduction - have short gestation periods, and produce large litters, which leads to quick population growth

specialized incisors - adapted for gnawing and allows them to eat a diverse range of plants

small size - allows them to hide easily, use minimal resources, and occupy ecological niches that larger mammals cannot

beahvaior - they have learned to coexist among humans & exhibit complex social behaviors, problem-solving abilities, and learning capacity. 

adaptation & evolutionary success - they exist on every continent expect Antarctica & can live in almost any habitat, including aquatic; their diversification reflects their ability to evolve new forms and lifestyles rapidly in response to ecological opportunities

Rodents are highly successful and diverse because they reproduce quickly, have specialized gnawing teeth, and are small enough to thrive in many habitats. Their adaptability, intelligence, and ability to coexist with humans allow them to survive almost anywhere on Earth except Antarctica.

what are species and why do we need them

species are populations separated into their own evolutionary paths, and no gene flow between them

hierarchical classification; if we had all the animals just laid out without any kind of organization, it would be overwhelming

what is the biological species concept vs the phylogenetic species concept

BSC: species are groups of actually or potentially interbreeding populations which are reproductively isolated from other groups

issues with this:

∙ not applicable to asexual reproducers

∙ not applicable to fossils

∙ potentially interbreeding

PSC: use phylogeny and look for monophyletic groups to help define what a species is  

issues with this:

∙ need a phylogeny

∙ needs other evidence 

prezygotic vs postzygotic in terms of isolation

prezygotic: before fertilization in egg

∙ different habitat preferences, different behaviors, different abilities for egg fertilization & sperm mobility

postzygotic: after fertilization in egg

∙ hybrids could not survive or they will survive but not able to reproduce (sterile)

threats for species survival

1. habitat fragmentation, degradation, & loss

2. disease

3. overexploitation

4. spread of invasive species

5. contaminants and pollution

6. global climate change

7. competing land use

what is CITES

CITES: Convention on International Trade in Endangered Species

∙ any country can be apart of it if it wants; there is some legal binding stuff if you want to remove yourself from it (185 currently)

∙ prohibits illegal trade of wild animals and plants

1. appendix 1 - all threatened species (all trade is illegal)

2. appendix 2 - species in risk of threat (trade is only authorized via special permit)

3. appendix 3 - species listed by country specifically 

CITES (the Convention on International Trade in Endangered Species) is an agreement between countries to protect wild animals and plants from being overexploited through international trade. In simple terms, it’s a global law that makes sure trade in wildlife—like animal parts, plants, or live animals—doesn’t harm their survival in the wild.

what is the Endangered Species Act & why is it important

what is the Endangered Species Act & why is it important

law passed by US Congress in 1973

mandates (things they have to do)

∙ list endangered sp domestically & abroad

∙ designate critical habitat for sp

∙ evaluate the impact of other agencies activities on sp

∙ formulate recovery plans for listed sp

∙ monitor the recovery of sp

∙enforce the laws prohibiting harming sp

The Endangered Species Act (ESA) is important because it protects plant and animal species that are at risk of extinction and helps preserve the ecosystems they depend on. It does this by identifying threatened and endangered species, prohibiting actions that harm them or their habitats, and creating recovery plans to help their populations recover and thrive.

The Endangered Species Act (ESA) is a U.S. law passed in 1973 to protect species at risk of extinction and the habitats they depend on. It requires the government to identify endangered and threatened species, protect their critical habitats, monitor their recovery, and prevent harm to them. The ESA is important because it helps conserve biodiversity and maintain healthy ecosystems for future generations.

around how many species are listed on the IUCN

~169,000

> 47,000 sp are threatened

41% amphibians

34% coniferes

44% corals

12% birds

27-36% terrestrial and marine mammals some are harder to study

how do you prioritize what to conserve

need to present argument of risk over certain organism and why the risk may threaten the organisms survival (lots of research)

need to understand relationships b/t organisms bc if they are so endangered they might be hard to study

important for the balance & the systems: indicator sp, umbrella sp, and keystone sp

threats

1. human growth → land use growth, food needs grow

2. habitat fragmentation

3. pollution

4. over exploitation

hair

hair develops from epidermal cells and are dead cells. to protect it, its surrounded by alpha keratin.

keratin is a structural protein found in hair, horns, claws, & hooves; it also protects the cells from stress & damage

basic hair structure:

the root follicle is embedded into the dermis. it is a living cell and pushes through the surface. theres a small muscle called the arrector pili that is a smooth muscle that you control subconsciously. if it contracts it causes your hair to stand up (goosebumps, chills). when it does this it can serve different func. like increasing the thickness of the coat of fur, makes animals appear bigger & alert → help defend pred.

medulla (hollow, helps buoyancy) → cortex(pigement cells) → curticle (protect everything inside)

coronal scales - lined up where one ends, one begins

imbricate scales - overlapping

Hair is made from epidermal cells that die as they grow and are protected by alpha keratin, a strong protein also found in horns, claws, and hooves that prevents damage. Each hair grows from a living root follicle in the dermis, which pushes the hair through the skin’s surface. A small smooth muscle called the arrector pili can contract subconsciously, making hair stand up—causing goosebumps in humans or making animals appear larger and more alert for defense. Hair structure includes the medulla (a hollow center that aids buoyancy), the cortex (which contains pigment), and the cuticle (an outer protective layer). Hair scales can be coronal, where each scale ends as the next begins, or imbricate, where scales overlap.

evolution of hair & fur

hypothesis of hair evolution:

early synapsids had scales that covered whole body that helped to protect body (made out of bet keratin) → therapsids/early mammals had loss of scales over time & started to separate, exposing skin which allows better sensory. with the exposed skin maybe some little divetes appeared allowing better sense of environment called sensory pits; also allows more flexibility → mammals - over time in sensory pits with all the nerves a follicle formed and there hair evolved. more hair forming and growing improves animals ability to sense environment, especially at night

function: increase number of follicles/sensory pits & increase number of hair in each follicle

functions of increasing density & significance:

insulation (slow heat loss & heat gain), sensory, protects skin, nerves, sensory pits, protection from predators (quills), visual (conceal, disrupt)

types of hair

1. Guard Hair

∙ longer & stiffer

∙ protection of insulator hairs that are under them

∙ wind break & another layer of insulation

∙ hollow medulla → helps buoyancy

2. Wool Hairs - underfur

∙ soft, short, densely packed

∙ main func of insulation, decreases heat loss & decreases excessive heat absorption

∙ also hollow in center to help buoyancy

3. Vibrissae (whiskers)

4. Spins/Quills

hair pigmentation

1. mechanical function of pigment

∙ components of hair itself gives color (melanin pigment)

      1. strength - more pigment → stronger color → more resilient & resistent to getting broken

      2. reflects heat - light hair helps to reflect heat in direct sunlight

      3. reflects UV - darker hair slows down absorption of UV rays & absorbs heat & rays

2. visual function of pigment

       1. concealing/ cryptic coloration - hide

∙ background matching (white in arctic); counter shading (dark on top & lights on bottom)

∙ disruptive coloration - breaking up outline of individual animals so they are harder to see (zebra); also against the environment (jaguar); also includes eye spots that hides the eyes in patches of fur

       2. conspicuous coloration - stick out

∙ aposematic function - color presents warning (skunk) 

∙ ocelli - patch on fur that looks like eyes that makes it look like it it hyper aware of surroundings

∙ weapon automimicry - something that lets prey know they have something that will hunt them; for antelope having stripes of face to accentuate their horns

∙ intraspecific communication - visual flags to communicate b/t species within sp

Pigment serves both mechanical and visual functions in animals. Mechanically, pigment such as melanin gives hair its color and strength—more pigment means stronger, more resilient hair. Light-colored hair reflects heat to help animals stay cool, while darker hair absorbs heat and slows UV absorption, offering protection from sunlight. Visually, pigment influences how animals appear in their environment. It can provide concealment through background matching (like white fur in the Arctic), countershading (dark on top and light underneath), or disruptive coloration (such as zebras or jaguars) that helps break up an animal’s outline. Pigment can also make animals stand out through warning colors that signal danger (as in skunks), eye-like spots called ocelli that deter predators, patterns that mimic weapons (like antelope facial stripes that emphasize horns), and markings used for intraspecific communication—visual signals shared within the same species.

hair replacement

1. angora growth type - continual growth

2. definitive growth type - set length where it will grow then stop

           ∙ continual molt - lose then replace; not extreme or crazy

           ∙ periodic molt - all hairs replaced

1. ontogenetic/postjuvenile - developmental; colors changing based on age

2. seasonal - changes quality and color of furr in animals to help better conceal

3. annual - more common in tropical area

integumentary structures

paws: keratinized hairless epidermis; helps to cushion as animal moves

claws: keratin derived; ancestral condition; scratch, evade pry, climbing & digging; evergrowing & worn down by abrasion

nails: modified claws, object manipulation; primates

hooves: derived from claws; more efficient locomotion; ungulates

true horn: bony core covered w a sheath of keratin

∙ only in Perissodactyla & terrestrial Artiodactyla

∙ only bovid artiodactyles have true horns

∙ grows continuously, unbranched, never sheds, both sexes

horns: differ slightly from true horns

ex: pronghorns - branched & keratine sheath sheds; giraffe - bony projections & covered in hair; rhinos - all keratin no bone at all

antlers: made entirely of bone, branched, new ones every year, while its growing its covered in skin, only in males; hormones helps grow & when they are done growing & its not mating szn the blood flow cuts off and induces the falling off of the bone

∙ only in Cervidae, but not all Cervidae have them

Integumentary structures are specialized body parts made from skin and keratin. Paws have a thick, hairless, keratinized epidermis that cushions movement. Claws are keratin-based and used for scratching, climbing, digging, and defense; they grow continuously and wear down with use. Nails, found in primates, are modified claws used for object manipulation. Hooves, derived from claws, improve movement efficiency in hoofed animals (ungulates). True horns have a bony core covered by keratin, grow continuously, are unbranched, never shed, and occur in both sexes of bovids. Other horns vary: pronghorns have branched horns that shed their keratin sheath, giraffes have hairy bony projections, and rhinos have horns made entirely of keratin. Antlers differ because they’re made of bone, are branched, shed annually, and are usually found only in male deer (Cervidae). While growing, antlers are covered in skin (“velvet”), which is lost once growth ends and hormone changes trigger the antlers to fall off after mating season.

Skin Glands

Skin Glands

exocrine glands - invagination in skin where fluid comes out and is secreted at skin’s surface

types:

1. exocytosis - tiny sacs called vesicles move to the cell membrane, fuse with it, and then excrete their contents out of the cell

∙ eccrine (merocrine) sweat glands - thin, watery sweat, not associated with hairs

immediately after birth, evaporative cooling, most common on surfaces that come into contact w substrate; ex: palms & soles of feet

2. apocrine - the tip of the cell is pinched off and it releases stinky sweat

∙ apocrine sweat glands - viscous sweat, located near hair

suction begins at puberty, oderless at secretion, converted to odorous by surface bacteria, common in areas where fur is less dense; ex: armpits

3. holocrine - a gland’s cells fill up with oil or other substances, then burst open to release their contents

sweat: apocrine & exocytosis/merocrine secretion

function:

1. getting ride of waste through kidneys

2. cooling or evaporating cooling, helps cools down body, breeze will come against skin and cause the wet mixture to evaporate at the surface of skin

3. localized in certain areas to help maximize cooling

4. lost in some (desert & aquatic)

5. produce a watery secretion

Skin glands release fluids that help with cooling, waste removal, and protection. Eccrine glands produce watery sweat, apocrine glands release thicker sweat near hair, and holocrine (sebaceous) glands secrete oils that lubricate and waterproof the skin. Scent glands, modified from sebaceous glands, produce pheromones for communication and marking territory.

Other glands

Other glands

Sebaceous (holorine)
function:

1. lubricate hairs (covered in oily substance to help water seal)

2. protect from abrasion

typically associated with hair follicles and are in close proximity 

Scent - modified sebaceous glands; holocrine secretion

∙ secretes oils that have odors (pheromones)

functions:

1. intraspecies communication

2. function to deter predators

3. mark territory

location varies: often in areas where they can rub it on something and leave it on somthing (legs, head, back)

Sebaceous glands are holocrine glands that produce oily secretions to lubricate hair, waterproof the skin, and protect it from abrasion. They are usually found near hair follicles. Scent glands are modified sebaceous glands that release oily, odor-producing substances (pheromones) used for communication within a species, marking territory, and deterring predators. Their location varies but is often in places where animals can easily rub and leave their scent, such as the legs, head, or back.

Mammary glands (apocrine)

origin - likely derived from sweat glands

hypothesis - all of the mammary gland traits started to evolve in the period of the therapsids & non-mammalian synapsids

step 1. the early egg-laying therians had a brood patch which is a patch with no hair that they can use to help insulate the eggs under the ground

step 2. sweat glands start to evolve in brood patch, wet sticky skin that increases heat to surface area transfer from mom body to egg

step 3. skin starts to folds around the egg like a pouch to further increase moisture content around egg

step 4. young hatch in pouch & start to lick it up might as well make what they’re liking up be nutritious → sweat glands start to become more milk like to nourish offspring but also pass on immunity

benefits: provides more heat transfer to young, nutritious liquid to lap up, immunity passed on

Mammary glands, which are apocrine glands, likely evolved from sweat glands. The process began with early egg-laying mammals (therapsids and non-mammalian synapsids) that developed a brood patch, a hairless area used to warm eggs. Over time, sweat glands in this area helped transfer heat and moisture to the eggs. The skin then began folding into a pouch, increasing protection and humidity. When the young hatched, they licked the moist skin, and the secretions gradually became nutritious and immune-boosting, evolving into milk. This adaptation provided better heat transfer, nourishment, and immunity for offspring.

arrangement

crib sheet: lec 13, slide 4

arrangement of nipples

arrangement of nipples

Marsupials - more common to have circular arrangements of nipples with one in the middle; 19-20 nipples

Placentals - 2 rows from pectoral to rump; can have special adaptations for dif animals like the beaver whose nipples are located laterally so they can nurse in the water; cetaceous dont have lips so they can squirt milk out

why do males not lactate too

males have other things that are their priority interms of fitness & making as many offspring as they can

why do they have nipples - evolutionary remnants aka leftover. in gestation when offspring are developing the default is female and its not until later that the male hormones take over (nipples develop before everything else)

potential question: which viviparity from test 1 do I support; use new stuff from lectures; 

is it that different that there would be two or are they similar enough that it supports 1 time

pouches & epipubic bones

old hypotheses that epipubic bones are to support pouch but not all marsupials have pouches but they have epipubic bones, reptiles have epipubic bones but no pouches, and monotremes have epipubic bones but no pouches

function of ep bones - not evolved to support pouch but maybe later used for it; most likely cite for ligament and muscle attachment for supporting mvm of lower body

might be an evolutionary remnant in monotremes, support evidence in why reptiles have them

male anatomy

paired testes that produce sperm (gametes) that fertilize eggs and produce hormones like testosterone

when reproductive szm hits, meiosis will be cued to turn dipolid cells to form haploid gametes (sperm). they are stored in testes and mature and move until transferred to the penis. males are constantly able to make and preoduce mature games for repro purpose

female anatomy

ovaries: pair of oval bodies, primary reproductive organ - mature games (eggs)

oviducts (fallopian tube): chanel for mature eggs to go to uterus

uterus: fertilized eggs will implant for embryonic development

cervix: connects uterus to vagina

vagina: opening to exterior

development of eggs happen while she in in utero developing in her mother. females are born with all of the eggs she will ever have. about 2 million

reproductive structures

monotremes

∙ mono - one hole (eggs, urine, fecal)

∙ infundibulum - location of fertilization

marsupials

∙ diadelphous reproductive track - 2 of everything (2 uteri, 2 vaginas, etc)

∙ form a pseudovaginal canal as a “fast track” for birth of young

∙ males have forked penis to deliver sperm to paired uteri

purpose: to allow for continuous reproduction and the ability to manage multiple offspring at different developmental stages

placental

∙ 4 types of reproductive tracks

∙ pair of ovaries & single vagina, but differ in # of cervix & uteri

Duplex - 2 uteri, 2 cervix, 1 vagina

Bicornuate - 2 uteri (uteri horns fused in common chamber), 1 cervix, 1 vagina

Bipartite - 2 uteri, 1 cervix, 1 vagina

Simplex - 1 uteri, 1 cervix, 1 vagina

sequence of events in repro

gametogenesis (maturation of games) → insemination/ovulation → fertilization → implantation → in utero development → partuition (birth)

ovarian cycle - stuff with eggs; development of egg in follicle → follicle bursts → release of ova from ovary → passage of ova to uterus

uterine cycle - series of changes in uterus to facilitate implantation of fertilized egg

1. estrus cycle

2. menstrual cycle

follicle - small, fluid-filled sacs located in the ovaries that contain immature eggs

Reproduction follows a sequence: gametogenesis (formation of sex cells) → ovulation/insemination → fertilization → implantation → in utero development → parturition (birth). The ovarian cycle involves the growth of an egg within a follicle, the follicle bursting to release the egg, and the egg’s movement to the uterus. The uterine cycle includes changes in the uterus to prepare for a fertilized egg to implant. Depending on the species, reproduction follows either an estrus cycle (reabsorption of the uterine lining) or a menstrual cycle (shedding of the lining). Follicles are small sacs in the ovaries that contain and nurture immature eggs.

what are the two types of uterine cycles

estrus cycle - after going into heat (estrus)

∙ uterine lining is reabsorbed if conception does not occur

∙ both marsupials & placental mammals

Anestrus - non bredding period

(1) Preoestrus - Anterior Pituitary releases FSH trigger growth of follicle as it is growing, ovary is producing estrogen → (2) Estrus - peak point of estrogen, the follicle ruptures and releases mature egg, surge of LH. can happen spontaneous or induced by insemination →  (3) Metestrus - presence of corpus luteum, release of progesterone that prepares uterine lining for implentation, (HP, LE) → (4) Diestrus - hormones level off after birth or non birth

menstrual cycle

∙ lining is shed at menstruation instead of being reabsorbed when pregnancy does not occur

∙ only some placental

∙ effectively same as estrus cycle, except no anestrus & diestrus period & if no fertilization of egg → endometriosis lining is shed  

hormones:

∙ estrogen - triggers ovulation (release of mature egg), “hormone of non pregnancy”

∙ progesterone - “hormone of pregnancy”

as estrogen increases = readying an egg for maturity, not pregnant, low progesterone

∙ Follicle Stimulating Hormone (FSH) & Luteinizing Hormone (LH) both stimulate the gonads

players:

∙ Anterior Pituitary Gland (produces FSH & LH)

∙ Ovary (follicles within produces Estrogen)

∙ Corpus luteum part of follicle that is left after egg has erupted (produces Progesterone)

The estrus cycle occurs after an animal goes into heat and involves the reabsorption of the uterine lining if pregnancy doesn’t occur. It happens in both marsupials and placental mammals. The cycle includes four stages: Proestrus, when FSH from the anterior pituitary stimulates follicle growth and estrogen increases; Estrus, when estrogen peaks, the egg is released, and LH surges; Metestrus, when the corpus luteum forms and releases progesterone to prepare the uterus; and Diestrus, when hormone levels stabilize after birth or no conception. In contrast, the menstrual cycle (found in some placental mammals, like humans) sheds the uterine lining instead of reabsorbing it and lacks anestrus and diestrus phases. Estrogen triggers ovulation and indicates non-pregnancy, while progesterone supports pregnancy. FSH and LH, produced by the anterior pituitary gland, regulate the ovaries—follicles produce estrogen, and the corpus luteum (the leftover follicle) produces progesterone.

blastocyst

blastocyst - early stage in developing mammalian embryo

successful fertilization → cells are dividing within egg (blastocyst)

monotremes - no implantation, blastocyst shell stays around the rest of cells as they divide

marsupials - blastocyst remains in permeable shell, little bit of gas exchange, for 75% of gestation time (shell membrane around developing young), other 25% the shell membrane rips apart and weak implantation of placenta

placental - two layers of blastocyst; inner of mass cells where fetus develops & outer layer called the zona pellucida which ruptures and frees trophoblast to cause tight connection w mother which forms placenta. placenta includesfluid filled membrane of amniotic egg

blastocyst can enter a dormant stage (embryonic diapause) in both marsupials & placentals

Placentals

In marsupials:

Choriovitelline Placenta - consists of Eudometrium of mom, chorion(outside layer), & yolk sac. mostly yolk sac which feeds young (all in blastocyst 75% ges time). last 25% the placental forms when the enzymes break blastocyst outer layer and the fertilized egg w dev fetus nesles in little spot in endometrium & placental forms (weak connection that why why are born so prematurely)

In placentals:

Chorioallantoic Placenta - main difference is the trophoblast facilities tight connection between mother & young

placental functions bc of trophoblast: (not in marsupials)

1. anchors fetus to uterus

2. transport nutrients from mother to fetus

3. excrete fetus waste

4. allow respiration between fetus & mother

5. produce hormones and serve as barrier bt immune sysms of young and mother

6. placenta also can protect young. since the young is ½ dad sometimes it can look like a parasite and the moms immune sysm can attack and kill it

summary:

∙ reproduction is costly, especially for placentals

∙ placental mammals have super high cost with gestation bc of connection & long reproductive times; placentals are born much more developed

∙ gestation in marsupials are not costly and not energetically expensive in females

∙ lactation over time increases in cost

∙ marupials can abort young if there is no resources available; estrous does not have a negative feedback → can have overlapping pregnancies; in placental when estrogen is high, progesterone is low so they cant get preg at same time

Marsupials have a choriovitelline placenta, made of the mother’s endometrium, chorion, and yolk sac, with the yolk sac providing most nutrients. This creates only a weak attachment, so young are born very underdeveloped and continue growing externally. Placentals have a chorioallantoic placenta, where the trophoblast forms a strong connection to the uterus. The trophoblast’s functions include anchoring the fetus, transferring nutrients, removing waste, allowing gas exchange, producing hormones, protecting the fetus from the mother’s immune system, and maintaining pregnancy. Because of this tight connection, placental reproduction is more energetically costly and involves longer gestation, but offspring are born well-developed. In contrast, marsupials have shorter, less costly pregnancies but longer lactation periods and can pause or end reproduction when resources are scarce.

breeding time:

cue into environmental conditions (temp, light, etc) to gauge when resources are good to breed

when resources are good:

fixed optimal season (predictable): fixed season like spring will be good time bc there are lots of resources

1. seasonally monstrous - breed one time & have 1 estrous cycle during that predictable time

2. seasonally polyestrous - when resources are plentiful → multiple estrous cycles, multiple litters per season

∙ shorter gestation & short developing time

3. seaonally monstrous w anticipation of optimal szn - breed prior to optimal szn occur; can pause their gestation time to wwait until optimal snz

irregular optimal season (unpredictable): resources are unpredictable & unknow when it will be a good time to breed

1. aseasonally polyesterous - no response to seasons; reproduction is occurring regardless of if resources are good or not;

2. seasonally polyesterous - as soon as resources are good they start breeding and as soon as they go bad they stop

better to be a marsupial mammal in an unpredictable environment bc gestation is short and cost is much later; bc if things go bad the female can save herself after birth and not let that young attach to a nipple or free it and keep the energy for herself, as opposed to the placental where the baby might die if not neough resources and the mother.

Breeding time in mammals is influenced by environmental cues such as temperature, daylight, and resource availability, helping them reproduce when conditions are most favorable. In predictable environments, species follow a fixed optimal breeding season. Some are seasonally monestrous, breeding once per season with a single estrous cycle, while seasonally polyestrous species have multiple cycles and litters during periods of high resources, aided by shorter gestation and development times. Others are seasonally monestrous with delayed implantation, breeding before the optimal season and pausing embryo development until conditions improve. In unpredictable environments, where resources vary, species may be aseasonally polyestrous, breeding continuously regardless of conditions, or seasonally polyestrous, reproducing only when resources become available and stopping when they decline. Overall, marsupials are better suited for unpredictable environments because their short gestation and lower prenatal investment allow them to abandon or delay caring for offspring if resources become scarce, conserving energy—unlike placental mammals, which face higher risks if resources fail during longer gestation.

1. synchronous - everything is time to work within the opinal breeding szn

2. sperm storage - males mate w females before snz → waits for optimal time to start everything ex: bats

3. delayed implantation - embryonic diapause; happens when repro szn isnt long enough

4. delayed development - slow rate of development once the optimal szn hits the development increases to time it right 

5. prolonged, gradual development - steady slow rate of development

reproductive costs:

female: gestation & lactation, females eggs are limited, larger, immobile; maternity certain (females know the offspring are theres bc they are gestating)

male: males can always produce more sperm; paternity uncertain (never know if they are successfully fertilizing the egg)

benefits:

1. produce offspring → pass genes on

2. reproductive success is maximizing your fitness with # of offspring produced

males - how many females can he inseminate

females - how many young can she produce with the most successful male

Sexual selection is a type of natural selection where individuals with certain traits are more likely to attract mates, causing those traits to become more common over time. It occurs through two main processes: intersexual selection, where one sex (usually females) chooses mates based on desirable traits such as size, color, or displays—sometimes leading to exaggerated features like large antlers through runaway selection; and intrasexual selection, where individuals (usually males) compete with each other for access to mates through fighting, dominance, or sperm competition. Some species show post-copulatory mechanisms, such as cryptic female choice (females control which sperm fertilizes their eggs) or the Bruce effect (females terminate pregnancies when a new dominant male arrives). Reproductive timing strategies include sperm storage, delayed implantation, delayed development, and prolonged development to match breeding with favorable seasons. Reproductive costs differ by sex: females invest heavily in gestation and lactation and have limited eggs, while males produce abundant sperm but face uncertain paternity. The main benefit for both sexes is reproductive success—passing on their genes by producing as many viable offspring as possible.

sexual selection

a form of natural selection where individuals with certain traits are more likely to be chosen as mates, leading to changes in the frequency of those traits in the population over time

1. intersexual competition - members of one sex choose certain mates of the other sex

∙ runaway selection (choosing the largest /best trait) ex: - Irish Elk antlers (maybe)

∙ traits are indicator models and linked to fitness; can be “handicaps” - decreasing fitness

2. intrasexual competition - males compete with each other to gain access to females

∙ pre-copulation: battles to have access to female; sexual dimorphism looks like traits that would benefit the male to win

⁃ sperm competition: either in favor of first or second male; more adv to be first male; males will often guard the females or copulatory plugs will help make it harder for second male

∙ post-copulation:

⁃ cryptic female choice - cryptic event where female will tuck away and choose which sperm will inseminate her

⁃ bruce effect - presence of novel male will abort other offspring and allow her to mate w better male; reduces infanticide (dominate male kill other offpring to mate again)

monogamy - one male & one female; not of lot of intrasexual competition; needed when both individuals are needed

polygamy: multiple mates, lots of intrasexual competition

1. polygyny - one male and more than one female; one male has high reproductive success; male overlap territory of multiple females

∙ resource defense polygyny - males defend resources that females need

∙ female defense polygyny - defend grp of females

∙ male defense polygyny - males constantly battling to guard females so no paternal care 

∙ scramble polygyny - males just mate w as many females as possible

2. promiscuity - multiple males & multiple females

3. polyandry - one female and more than one male

semelparity - animals reproduce one time only

Social systems in mammals involve living and cooperating in groups, offering benefits like predator protection, cooperative foraging, shared parenting, and better learning for young, but also costs such as competition, aggression, disease, and higher visibility to predators. Mating systems range from monogamy (one pair) to polygamy, including polygyny (one male, multiple females), polyandry (one female, multiple males), and promiscuity (many partners). Simple social systems are temporary, often same-sex groups with dominance hierarchies and limited cooperation. Complex social systems are long-term, involving both sexes, multiple generations, stable hierarchies, communication, and division of labor. The most advanced form, eusociality, has one breeding female and non-reproductive workers (as in naked mole rats). Overall, sociality evolved through natural selection because cooperation and group living improve survival and reproductive success more than solitary living.

Social Systems:

advantages:

1. antipredator benefits - increases vigilance to keep watch for preds, prey dilution (low risk of bein preyed upon), predator confusion (zebras), group defense against other herds or preds

2. foraging benefits - group hunting, sharing information of new spot for grazing, reduced stealing of food of individuals

3. mate choice benefits - increase choice of mates & increase repro success

4. physiological benefits - shared thermoregulation, more efficient use of limited shelter

other: division of labor among specialists, reduced aggression, richer learning environment for young

disadvantages: issues of sharing resources

1. predator cost - increased visibility to predators, increased attack rate

2. foraging cost - increase stealing, decrease food availability, increase aggression

3. mating costs - increases competition for mates, increase rate of infanticide

4. increases risk of diseases and parasites

types: (complex as it goes up)

individuals live in a group in a cooperative manner, often sacrificing personal gain

ex: alarm calling, upbringing of young, alliances

1. Simple Social Systems - temporary, non-reproductive (sometimes all same sex), dominance hierarchy, can bring non traditional groups together

2. Complex Social Systems - permanent, over time in terms of number of individuals and identity of them, division of labor, communication witihin sp, dominance hierarchies, adults of both sexes with multiple generations of young and some will leave to start their own social sym.

3. Eusociality - one breeding female & working casts below, reproductive & non-repro individuals (naked mole rats)

why would it evolve: sociality evolves through natural selection acting on individuals that gain direct or indirect fitness benefits from living and cooperating with others. Whether through kin selection, reciprocal altruism, or mutual benefit, sociality persists when cooperation enhances reproductive success more than solitary living would

behavior:

activity patterns:

Circadian patterns (cycles based on a 24-hour light/dark cycle)

∙ universal in mammals & vary among sp

∙ shift seasonally

∙ can be endogenous (internally, master clock made of cluster of neurons) or exogenous (externally, day length, temp)

Circannual pattern (1 year cycle)

∙ reproduction

∙ migration & hibernation

exogenous cues include: day length, changes in food abundance, rainfall, temp

use of space:

home range - where an animals travels in its normal activities; territory = portion of the home range that its actively defending

size of home range depends of species size; bigger animals = bigger home range; but maybe be irregular depending on good resources; also depends of szns too

foraging

selection favors foraging behavior

caching - food storage & moving food storage one place to another

shelter building: underground (fossorial), in trees, under leaves, in ponds

benefits: protection from predators, more stable temps, places to store food

communication - used over time bc they useful at conveying information

1. visual - body posture, facial expressions, anatomical structure(weapon automimicry, coloration)

2. olfactory

∙ pheromones - between members of same sp

∙ allomones - different sp

3. auditory

∙ ultrasonic (high freq; cetaceans

∙ infrasonic (low freq; large animals, elephant)

4. tacticle - touching like grooming

Many mammals follow circadian (daily) and circannual (seasonal) rhythms influenced by environmental cues like daylight, temperature, and food availability. Conservation biology focuses on protecting species and their habitats. Agencies such as the IUCN, U.S. Fish and Wildlife Service, and CITES assess extinction risk. The Endangered Species Act of 1973 protects threatened and endangered species by listing them, designating critical habitats, evaluating human impacts, developing recovery plans, and enforcing protection. CITES regulates international wildlife trade to prevent overexploitation.