Detection methods

wildlife biology

what are the purposes

detection of species - species of prescence

counting of individuals - abundance estimation

investigate species biology or ecosystems - pure or applied research

species presence/absence

useful for investigating the geographic range of a species, distribution within its range and conservation status

can be used with habitat variables to identify variables that predict a species distribution

can also be used to compare diversity at a community level

Abundance

useful for assessing conservation status relating to population size

density of animals in differan habitats, experimental treatments, locations etc can be compared

can also be used in applied research on ecosystem ecology

investigate species biology or ecosystems

useful to establish population biology and demographics like reproductive rates, survival, mortality, population structure, characterizing diet, behavior or movement patterns of species

decribing breeding and other life history characteristics examining genetic structure, determing prevelance of an infectious dsease

what are the two detection techniques

direct and inderect

direct detection

• non invasive - direct observational

• invasive - capture and handle

inderect detection

non-invasive - detect/collect sign - calls, tracks, and traces of animals

what may you need to obtain to work as a wildlife biologist? what may you also need to comply with

1. a license to undertake the scientific research

2. other licenses

3. Animal ethics approval from the institution

may need to comply with

1. federal and/or state fauna survey guides

2. requirements of the animal welfare act

when are observation methods used

used on species that are readily visible in the habitat

when surveying an area to determine if species are present

can be used to quantify sightings in an area

estimate abundance

what are some observational methods

detecting animals in aggregations - detect clumps using aerial surveys

line transects - large conspicuous mammals

spotlighting - for conspicuous but nocturnal species - usually arboral that cant be trapped

camera trapping - heat and motion sensing cameras, used for medium to large reptiles and mammals

bird observational methods

transects -

• line transect - line traveled by observer covering area of unlimited width

• strip transect - line traveled where all birds within fixed width are recorded

point counts - 

surveyor at a point surveys the surroundings for a fixed, predetermined amount of time

area searches -

quadrat survey in which the observer moves throughout for a fixed amount of time detecting all birds once

detection function

calculated based on the probability of detection at a given distance from the line

how can accuracy be improved

repeat surveys of the same location

points, lines, quadrats should not overlap

advantages of observational surveys

animals are not handled directly

low researcher effort, time and cost effective

researcher experience (no training or additional license needed)

good for assessment over a large number of sites

good for assessing occupancy and population abundance

can adjust for detectability but most give indices of abundance only

disadvantages of observational surveys

low reolution of information collected

clear protocols for observation needed to standardize

capture and handle

used when cryptic animals are too small, active at inconvenient times, coloration, or their behavior

search and hand capture

used for reptiles and amphibians

time constrained - actively searching in a given area for a predefined amount of time

area constrained - actively searching with a predefined quadrat

most useful for presence or absence and for providinf initial data on types of microhabitats

aluminum folding box traps

used to capture animal for live-capture and release

used for small mammals, reptiles, and amphibians

cage traps

can capture one individual at a time

small-medium sized animals

pitfall traps

interception trap to catch reptiles, frogs, and mammals

good for secretive fossorial species

funnels traps

reptiles large and small

can be deployed where pits cannot be dug

mist netting

capture low flying birds and bats

harp traps

interception trap used for bats

accuracy of trapping methods

some individuals are more trappable than others

adjust method to suit the species

high fraction of individuals need to be trapped to get reliable abundance estimates 

some species caught in multiple traps, some in only one

advantages of hand trapping

establish presence/absence and abundance 

can account for detectability if using mark recapture estimates

collect high resolution data on individuals

disadvantages of hand capture

intensive, multiple trapping sessions, high researcher effort and cost

disturbs animals

search and capture can be destructive

Detection sign - calls track and traces

detecting signs of animals rather than the animal itself, can be useful supplementary method

suitable for establishing species occupancy and in some cases establishing population index

what tracks and traces are observed

scats

diggings

tracks

feeding residues

hair

nests

calls

hair tubes

employ collection tubes that are slightly larger in diameter than the species being studied

animals go through and fur is stuck on sticky tape

collected after about a week

counting nests in colonies

counting number of nests (fresh) can be an index of population size

acoustic detection

can be used to detect species at locations

accuracy of sign detection methods

detection of signs is limited in its accuracy and applicability and needs to be interpreted with caution

no information in gender identity, age, reproductive status, recommendation that other measure are used to consolidate research

advantages of detection methods

animals not handed directly

low research effort

good for assessment over large number of sites as supplementary method to ID suitable site for further survey

good for assessing occupancy

can collect samples which can be further studied

can detect species not readily trapped

disadvantages of detection methods

low resolution of information collected

data must be interpreted carefully

detectability compromised

estimating abundance - presence/absence only for most methods

abundance from population index only and only with quantitative sampling approach

marking techniques

tags, bird bands, ear notching, UV florescent tattoo ink or visible implant elastomer, passive integrated transponder tags, recognition without marking

why do they mark them?

indicate that this animal have been previously captured

give the animal an individual identification number

provide DNA sample

what are the purposes of marking indiviuals

estimate population size

• known to be alive

• mark-release-recapture or indices

study life history and reproduction

study movement patterns

tags

including ear tags for medium-large mammals and flipper or fin tags for turtles and fish, these can be applied using specialized, custom made pliers

Bird bands

metal rings enclosed around the legs of birds these are applies with customized pliers

ear notching

one or more pieces of tissue are removed from the margin of the ear

UV fluorescent tattoo ink or visible implant elastomer (VIE)

injected with small needle under skin - ventrally in reptiles and amphibians, on tail in mammals

VIE tags are implanted under translucent tissues, but remain visible

Passive integrated transponder (PIT) tags

used on mammals and some reptiles, frogs, fish

chip injected beneath the skin using a syringe

microchip - infinite life

recognition of individuals

pattern recognition and use of digital catalogues can for used for fin/flukes of marine mammals and skin color in some amphibians