Mammalogy - Lecture notes 1-20 PDF

Preview

Summary

All lecture notes....

Description

Mammalogy   

Morphology test September 5th – Morphology labs August 22nd & 29th Learn 80 mammals by skin and skull – use only scientific names Send 1st & 2nd choice for Grad Lecture to Dr. Leburg

Foundations of Mammalogy  Cave paintings of mammals that directly impact existence – food source and predators  Greeks/Romans/Aristotle = 1st people to make educated observations of the natural world – but most lost in the middle ages  1600’s/Renaissance = importance of natural world in West o John Ray 1650 = developed definition/organization of mammals – “animals with breasts or mammates” o 1693 definition includes other very general characteristics which do not only apply to mammals o Carl Linnaeus 1758 = proposed system of classification, naming and organization o Charles Darwin + Alfred Wallace 1958 = theories of natural selection = revolutionized biology of organisms Westward Expansionism Drives Mammalogy in the Early U.S.  Beaver pelts lead to mammal exploration  Lewis & Clark tasked with taking field notes of animals and plants while searching for a passage to the west coast  Bachman 1850 = 1st book of mammals in North America “viviparous quadrupeds of North America Three Branches of Wildlife Exploration  Museum and Systematics o Baird 1870 = book of mammals, founder of Smithsonian Museum of Natural History, named many organisms  Wildlife Management o Merriam = U.S. Biological Survey – group of biologists tasked with controlling predators  Decrease predators = increase hunting animals for us  Life Zone Concept = increasing latitude/altitude leads to faunal changes, explained by changes in temperature  Splitter = every change in morphology means a new species (identified 79 species of brown bear, only 1 species today) o Aldo Leopold – founder of modern wildlife management  Book on game management = maximize animal populations for human benefit  Sand County Almanac = land ethic which includes people as part of the system  Academic Biologists o Louis Agassiz – U.S. Natural History Museums & opposition of Darwin (believes in creationism) o David Starr Jordan – Supports Darwin o Joseph Grinnell – father of mammalogy and ornithology, developed the niche concept, wrote extensively for conservation through a scientific lense o E Raymond Hall – trained 80% of mammologist during his time, mammologist for evolution and natural history

What is a Mammal?  Phylum Chordata o Dorsal nerve cord o Gill slits o Notochord o Post anal tail  Sub-Phylum Vertebrata o Central nervous system, spinal cord, brain o Dill arches evident during development  Clade Tetrapoda o 4 limbs – essential during transition from aquatic to terrestrial o 5 digits or less  Amniotes o Member encloses and protects embryo in fluid o Critical for birth on land  Synapsids  Reptiles v Mammals o Trend towards simplification of skeleton in mammals  Conserve energy and allows for better movement  No ribs in abdomen  Spine is designed for dorsal/ventral flexing  Enlarged pelvis and pectoral girdle  Enlarged brain case  Legs oriented below spinal column v legs splayed (reptiles)  Decreased muscles at the ends of limbs (movement facilitated by tendons), but increased muscles in pelvis/pectoral girdle  1 bone in lower jaw = dentary  articulation of jaw in reptiles = quadrate and articulus – these bones are of the inner ear in mammals (incus and malleus)  Skull ridges in mammals for muscle attachment  Sagittal crest, lamboidal ridge, zygomatic arch  Well-developed facial muscles help to convey emotions/communicate  Reptiles – 1 occipital condyle, Mammals – 2 occipital condyles (large skull with increased muscles, limits movement of head)  Mammals stop growth @ reproductive age (asymptotic growth) and growth from epiphysis of long bones  Males growing larger in many species  Switch off growth to reproductive mode (typical of endotherms) Traits of Mammals  Teeth o Enamel – one of the hardest biological structures we know

2

o Dentine – forms bulk of body of the tooth – interactions between enamel and dentine is related to animal foraging o Pulp cavity – supplies blood through root canals – structures close as the animal reach maturity o Cementum – sticky material that holds tooth in the cavity o Labial/buccal – side of tooth near the cheek o Lingual – side of tooth near the tongue o Anterior – front of mouth o Posterior – back of mouth o Occlusal – where a tooth meets another tooth o Primitive reptiles = undifferentiated teeth, not a lot of cusp structure and similar shape throughout the mouth o Mammals = differentiated teeth, tooth structures change across species o Incisors – pre-maxila (front), nipping/cutting, huge variation across species, usually uni-cusp, Placental mammals have 0-3/quadrat, Marsupials have up to 4/quadrat  some grazers only have incisors on the dentary (bottom jaw)  rodents have ever-growing incisors with enamel on the front only to maintain a sharp edge  tusks are modified incisors o Canines – maxilla, 0-1/quadrat in modern mammals, piercing,  Lobed canine possible, but usually uni-cusp  Very large in carnivores for killing  Large canines can also be due to sexual selection and are much more evident in males – ex: baboons  Some canines may look very similar to incisors (incisiform)  Many herbivores have a large space between incisors and pre=molars, canines can be lost, due to extension of face for grazing o Pre-Molars and Molars – maxilla, sometimes distinct differences between pre-molars and molars (if not = molarform teeth), chewing/shearing,  Tribosphenic molar – upper jaw, 3 cusp structure, found in early mammals as well as opossum today (eats everything)  Brachyodont – low cusp teeth (omnivores)  Hypsodont – high cusp teeth (herbivores)  Bunodont – rounded cusps on molars (Omnivores - humans, chimps, bears, raccoons, etc.)  Lophodont – cusps form ridges of enamel with dentine in between running from the cheek towards the tongue (herbivores – tapirs, rodents) if they are brachyodont then they are usually ever-growing, if they stop growing then they are usually hypsodont  Loxodont – extreme lophodont (elephant)  Selenodont – ridges form cresents which run along tooth row (cow, deer, horses, ungulates) usually hypsodont  Common specialization in carnivores = carnasials (first lower molar and last pre-molar on upper jaw) used for tearing and shearing meat, hypsodont, sectorial (carnasials as a set of teeth)

3





4

o Diphiadont – two sets of teeth (one that comes in during development and one that comes in during maturation) o Teeth in juveniles = deciduous teeth (incisors, canines, pre-molars) o Some mammals are monophiadont – toothed whales, duck-billed platypus, shrews o Plyphiadont – cheek teeth move forward as front ones are wore down (elephants – 6 cheek teeth) o Dental Formulas  Incisors, Canines, PreMolars, Molars  Upper and lower jaw divided by line  Only do 1 side of face  Add up and multiply by 2 = total # of teeth  Humans 2/2, 1/1, 2/2, 3/3 or 2 1 2 3 / 2 1 2 3  Primitive Mammals (44) 3 1 4 3 / 3 1 4 3  Basic Marsupial (52) 5 1 4 4 / 4 1 4 3  White Tailed Deer (32) 0 0 3 3 / 3 1 3 3 Mammary Glands – provide nourishment to young, not all mammals have nipples (duck-billed platypus) and others have very specialized nipples (marine mammals), anywhere between 2-19 nipples which correlates with number of young per litter o Pectoral/Axial, Inguinal (pelvis), Abdominal o Marsupials have pouch with nipples inside, young are born underdeveloped and transferred to marsupium to feed and develop o Related to sweat glands (eccrine + apocrine) hugely variable across mammal species  Apocrine – under control of hormones, gave rise to mammary glands, gave rise to glands that produce earwax, pheromones, located at hair follicles  Eccrine – sweat  Interactions of secretions with bacteria = odor Hair – epidermal cells strengthened by keratin (nails, horns, scales) o Scales on zoomed in hair are unique to species o Cortex = body of hair, grows from dermis (hair follicle) associated with sebaceous glands (oil to keep hair flexible/waterproof) o Muscles around follicle can make hair stand on end o Guard hairs (porcupines = modified) + underfur (provides insulation) o Helps animals to survive at extreme cold temps – blubber in marine mammals o Molting – shedding fur seasonally (temp change and/or camouflage) and as they mature  Seasonal molting run by changes in day/night length – climate change is hurting this (ex: brown snowshoe hairs on white snow) o Individuals of the same species can be of different colors depending on habitat (ex: chaetodipus on lava flows v desert) o Counter shading – dark dorsal surface and lighter colored under surface o Vertical stripes tend to make an animal look bigger than it is, and helps to break up animal in vertically structured habitats (grassland) o Black face masks – aid in reflection of light, hides the eyes o Albinism – no color pigment (mutation of 1 gene)

Melanism – all black/dark colored (more common than albinism) Aid in buoyancy, gliding (flying squirrel), swimming (aquatic shrews) Whiskers + porcupine quills have tactile functions Warning Coloration & standing on end Food collection – some bats have modified hair on faces to collect pollen . 3 Hypothesis  hairs developed from sensory systems associated with the base of the scale  hairs developed from alteration of keratin expression of distal end of scale  hairs developed completely independent of scales Endothermy – not unique to mammals, but drives behavior/functions of mammals o Maintains a fairly constant body temperature – Homeostasis o Shed heat through conduction (direct loss), convection (moving air) and evaporation o Reaction rates of the body are driven by temperature (too low & too high = slow rates and adverse effects) o Expensive to maintain due to high loss of energy to heat, but = ability to active over a wide range of temps/times of day  Hard to be super small and endothermic due to increase surface area  90% of energy budget to thermoregulation  Need long term + more stable food sources  Mammals represent a small proportion of biomass in many landscapes o Metabolic Rates  Thermal neutral zone = don’t need to expend extra energy to maintain body temperature  Lower Critical Temperature and Upper Critical Temperature = must increase metabolic rate to maintain body temp = expending energy  Generation of heat = shivering & metabolism of brown fat (neck, shoulders, major organs)  Dissipation of heat = sweating, panting, brain cooling (artiodactyls – cool venous blood returning from the nose can flow to the cavernous sinus which will cool arterial blood flowing to the brain – cools brain during rest to reduce water loss through panting)  Lower Lethal Temperature and Upper Lethal Temperature = thermal stress which can lead to death (hyperthermia, hypothermia) o Most mammals try to maintain body temp near 38’C o Bergman’s Rule – body size tends to increase as you increase latitude (decrease in SA:V) – endotherms only  Larger animals need more food, but less energy per unit body mass to maintain metabolic rate  71% of mammals with north/south trend in size are largest in north  selection for big animals in north since other animals are big (less likely to be eaten)  more food for animals in the north (Michigan v texas) o o o o o o



5



6

o Allen’s Rule – shape is driven by endothermy – There are more compressed body shapes in colder environments o Heat Exchange Systems  Cold venous blood runs along warm arterial blood, cooling down arterial blood and warming up venous blood to minimize heat loss in extremities  Dilation of capillaries near the surface to lose heat and constriction to conserve heat o Length and thickness of fur  Decrease length in smaller mammals – limited by size  Less insulative value in hair of tropical mammals  Wet = massive decrease in insulative ability o Blubber  Forms a fatty layer around the core of the body o Behavior  Seek shelter from winter conditions  Migration – short or long  Alter environments to minimize heat loss – den, burrow, etc.  Huddle – using the group to create a core temp, reduce SA  Basking  Hibernation – profound torpor often seasonal, associated with day length reductions and hormonal changes v Torpor – short term reduction of body temp associated with reduced ambient tem and food  Only found in small mammals who would not benefit from expending energy (no food/hard to maintain body temp)  Bears = winter dormancy – not as profound as hibernation  Saves energy by decreasing metabolic rate  Arousal takes time and significant energy, but occurs every few days in order to defecate and forage on stored food - demands for arousal are scaled with body size which is why we do not see large mammals hibernating  Estivation – periodic torpor in hot conditions when food resources are limited o Water loss in arid environments  Brain cooling – see metabolic rates, Lower/Upper Critical Temps  Diet – carnivores can get all water from diet, eat cactus, rodents can get all water through oxidation reactions from eating grains  Concentrated urine due to Loop of Henle in Kidney  Extensive membranes in nasal cavities to help retain water  Thermal windows to dissipate heat without losing water  Adaptive hyperthermia – allow bodies to become hyperthermic for short periods of time  Ground squirrels sit in shade then run out to forage in sun = hyperthermia for short periods  Camels become hypothermic at night then slowly heat up throughout day to become hyperthermic before cooling down again as night sets o Graph on maintaining homeostasis – Humans o Endothermy and Heterothermy has evolved several times in separate lineages Circulatory System











o Developmental pathways are unique, but 4 chambered heart itself is not unique to mammals o 2 atrium + 2 ventricles, powerful o Tri- cusp valve that separates right and left ventricle – unique o Heart rates decrease with size of mammal o A-nucleated erythrocytes = concave shape = aids in oxygen transport Respiratory System o Diaphragm – unique to mammals – no direct comparison to other organisms  Contraction = diaphragm pushes down, reducing pressure on lungs causing air to rush in  Relaxation = diaphragm moves up into natural shape, putting pressure on lungs leading to exhale Brain Structure o Well-developed cerebral hemisphere = complex behavior o Primates + elephants have largest brains scaled to body size Vision o Very few mammals see color – some rodents, some primates – important in mating displays, foraging on fruits, etc. o Some rodents and bats can see ultraviolet – help to visualize urine marks? o Vampire bats see in infrared o Tapetum Lucidum – reflective layer behind retina which aids in enhancing vision in low light – nocturnal animals Hearing o Arrangement of bones in ear + pinna (external to focus sound waves to auditory bones) – unique o Incus evolved from quadrate bone o Malleus evolved from articular o Stapes Reproduction o Most mammals have a relatively sophisticated placenta (exceptions are monotremes which lay eggs) o Marsupials have a complex uterus that has medial and lateral vaginas, the placenta is formed from a yolk sack o Prototherians, metatherians and eutherians o Most mammals lack a true cloaca (reproductive, urinary, excretory tracts converge to 1 opening)

Wildlife Diseases  Disease = abnormal condition affecting the body of an organism, clinical condition which adversely affects health  Parasitism = symbiosis in which one species benefits at the expense of another o Micro – carry out its lifecycle and multiply within a host o Macro – some part of the lifecycle occurs outside of the host o Ecto – living outside of the skin (on top) o Endo – within the body system  Zoonoses – diseases transmitted from nonhuman animals and humans or between any two species

7

   



 

 

8

Enzootic – disease persists in a population and affects humans at low constant levels Epizootic – diseases which exceed normal levels Immunological tests or PCR to detect diseases in organisms Coevolution – evolutionary interactions between a host and its pathogens o Pathogens may become more/less virulent o Hosts may develop resistance to pathogen o Red Queen Hypothesis – we are constantly coming up with new mechanisms to deal with parasites, but parasites are also evolving – you must keep running just to stay where you are o Pathogens are generalists and organisms develop unique responses to which different lineages of the pathogen respond to those developments = specialized pathogens to specific organisms Why do diseases kill hosts? o Needed for transmission – in some cases o Generalist, highly transmissible = no selective pressure to become less lethal o End up in the wrong host, but not in their specialized host White Nose Syndrome, Tasmanian Devil Facial Tumor, Distemper + Black Footed Ferret Biological Control o Rabbits introduced to Australia in late 1800’s and spread like wildfire across the continent o Myxoma virus introduced to control rabbits  Nearly 100% virulence at start, but over time = less virulent and increased resistance in rabbits o Rabbit Hemorrhagic Disease  Nearly 100% virulence at start, but over time = less virulent and increased resistance in rabbits Abomasa parasite counts in deer = parasite load correlated with health of heard, overpopulation = dramatic increase in parasite load Nonvector Zoonoses = direct transfer from one mammal to another o Rabies – multimillion dollar industry in U.S. for preventing transmission to humans  High risk in Asia, Africa, Mexico and Northern South America  20 deaths in U.S. since 1980 – 50,000 deaths/year in India  incubation in raccoons is 3-7 weeks before animal will show signs of sickness, after which it will usually die within 7 days  Strains for Raccoons, Skunks/Foxes, Mongooses, Bats (several widespread strains) – but can be transmitted across species  Ferious (agitated) form and Paralytic (dumb) form  5% of bats tested have rabies (bats that are tested are usually showing symptoms of rabies) – actual % is much lower  series of 3 vaccinations for people, but do not totally protect- if you are bitten then you still have to go to hospital to get a booster and the chances are very low  Primary vectors to humans = bats and carnivores, many other animals are susceptible though!  Embed rabies vaccine in bait and lay out for wild animals – seems to have worked to hold the raccoon rabies to the east coast – really expensive effort o Leprosy

Also known as Hansen’s disease Infects over 1million people mostly in Africa and Asia Old world disease which arrived to South America with the Europeans in 1492 Caused by bacteria Carried by Armadillos – 20-30% in Louisiana populations – humans gave it to them first  Die quickly  Animal of mammalian lineage which includes anteaters  Cooler body temperature Viral Hemorrhagic Diseases o Diseases that cause internal hemorrhaging o Hantavirus  1993 huge outbreak in  particularly lethal in Navajo Indians = press coverage  particularly wet year = super production of pine trees = increase in rodent populations  exposure through mouse droppings/urine  flu like symptoms, fever, vomiting, diarrhea, aches/pains, lungs begin to fill with fluid (only severe infections which can lead to death)  principle carrier of disease = peromyscus maniculatus HIV, Ebola, Marburg o HIV evolved in primates and jumped species when people were hunting monkeys for bushmeat o Primates are an obvious source of diseases which people have been exposed to and can be affected by o Ebola and Marburg have jumped from primates multiple times and kill rapidly = no long lasting reservoir in humans or primates  Circulate in cave dwelling fruit bats (reservoir) without being lethal  Mortality rate of 50-90% Biology of Histoplasmosis o Fungal Disease – Histoplasmosis o Birds and Bats = reservoirs o Be weary of lots of droppings in a confined space o Lung infection, but us...