Terrestrial Vertebrate Surveys some design and analysis considerations Mark Cowan Biogeography Program Science and Conservation Division Department of Parks and Wildlife
What entities to measure and how they should be measured is best guided not by a generic framework but rather by well defined and scientifically tractable questions (Lindenmayer and Likens 21)
Background to the presentation Field survey techniques Recording the vertebrate fauna assemblage in a potential impact area trapping and trapping layout patterns, digging in effects, trap hygiene, trap deaths, disease risk Trapping site layout design considerations for assemblage detections, Drift fences Pit traps Funnel traps Cage traps Aluminium box traps Incidental observations Spotlighting Format of the presentation General considerations of survey design and approach Methodologies employed for mammals and reptiles Considerations of ethics Basic analytical considerations
General considerations Standards for vertebrate surveys Project objectives are met by appropriate design and sampling methods Considerations of sampling Stratified Replicated Repeatable Verifiable Most information for least effort
General considerations Site Selection Examination of available spatial data. Digital elevation models Landsystem mapping Vegetation mapping Satellite imagery Aerial Photography Surface geology Fire History Climate data Reconnaissance of predetermined sites
General considerations Species group and major survey detection methods Group Small Mammals < 3g (eg Sminthopsis) Medium Mammals <25g (eg Isoodon) Large Mammals >25g (eg Petrogale) Bats (Megachiropter a) Bats (Microchiropter a) Pit tra ps Funn el Trap s Medium Aluminiu m Box Large Aluminiu m Box Cage Spotlighting from vehicle Spotlighti ng on foot Head torchin g Diurnal Observat ion/ Active Searchin g Search ing for tracks & signs etc Soun d/ calls Recordin g Techniqu es including Anabat X X S S S S S S X X X X S X S S Mist nettin g Har p tra ps Tri p line s Rem ote came ra X X X S S X X S S X X X S S X X X X X Hai r tub es Birds S S X S X S S Small snakes <45cm(eg Parasuta) Medium-Large Snakes> 45cm (Demansia) X X X X X X X X X X X S Small medium Lizards <15mm(eg Pogona) X X S S S X X Large lizards>15mm (Varanus) S X S S S S S X X Frogs X S S S X X S X X Environmental Protection Authority and Department of Environment and Conservation (21) Technical Guide Terrestrial Vertebrate Fauna Surveys for Environmental Impact Assessment (eds B.M. Hyder, J. Dell and M.A Cowan). Perth, Western Australia. http://www.epa.wa.gov.au/epadoclib/3281_faunatechnicalguide.pdf
General considerations seasonal capture of reptiles and mammals 4 Captures per 1 trap nights 35 3 25 2 15 1 reptiles 5 Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Captures per 1 trap nights 14 12 1 8 6 4 2 mammals Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month
General considerations humidity and temperature Interpolated surfaces for skinks and geckos from the Murchison Bioregion Data derived from more than 2 trap nights using 2666 captures for skinks and 3743 for geckos Skinks show moderate increases in activity from temperature alone A combination of humidity and temperature are associated with high captures of geckos
General considerations moonlight 3 Mammal capture rate in October and November Frequently asserted that bright moonlight decreases mammal captures. Complex to analyse Examined pit capture rates in two seasons No significant change with moonlight in either season. Captures per 1 traps Captures per 1 traps 25 2 15 1 5 45 4 35 3 25 2 15 1 5 R² =.318 1 2 3 4 5 6 7 Moonlight in minutes Mammal capture rate in March and April R² =.671 1 2 3 4 5 6 7 8 Moonlight in minutes
General considerations Summary Methodologies must be appropriate to the objectives of the study Considerations should be given to Knowledge of the natural history Trophic niche of the group considered Seasonality Temperature Humidity Moon phase
Methodology Pit and funnel traps Distance between traps Alternating trap types Trap type efficiency Continuous lines versus individual traps or other designs Number of traps per site Number of trap days
Methodology Pit trap position Capture rates in relation to trap position Data is from Lorna Glen and accumulated for 48 pit lines Inside traps capture significantly more than end traps End traps capture ~ 2/3 of inside traps Total captures 5 45 4 35 3 25 2 15 1 5 1 2 3 4 5 6 Trap number Dasyuridae Geckos Muridae Scincidae
Methodology Buckets, PVC Pipe & Funnels Differences in capture rates between buckets and PVC pipe for all fauna (4 locations and 23 surveys) 1 9 8 7 percent 6 5 4 3 2 1 % of individuals in buckets % of individuals in PVC pipe % of species only in buckets % of species only in PVC pipe Differences in capture rates between buckets and funnel traps 1 9 8 7 Percent 6 5 4 3 2 1 % of individuals in buckets % of individuals in funnels % of species only in buckets % of species only in funnels
Methodology Number of pits 9 Data from a species rich environment 8 7 Predicted total number of species from the Chao1 estimator is 82 Number of species caught is 79 for reptiles and small mammals Number of species 6 5 4 3 66% 62% 53% 43% 12 pits 9 pits 6 pits 3 pits Increasing number of traps increases species accumulation 2 1 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 17 18 19 2 21 22 23 24 Survey period
Methodology captures on sequential days 6 mean reptile captures on successive days in pits 13 survey periods with 24 sites and 12 across two lines at each site 443 reptile captures mean captures 5 4 3 2 1 1343 mammal captures There is little reduction in capture rates for reptiles Mammals show a marked reduction mean captures 45 4 35 3 25 2 15 1 5 1 2 3 4 5 6 7 day mean mammal captures on successive days in pits 1 2 3 4 5 6 7 day
Methodology Mammal trapping Focus on Elliott traps and cages Density, type and arrangement of traps has to reflect objectives of survey Effective for larger mammals and rodents, less effective for small dasyurids (eg S. longicaudata) In areas where no large mammals remain pits are generally better. Variable species response to trap type and timing
Mammalian considerations Elliott captures on successive days Data from four surveys with 12 Elliott traps at each of 24 sites 14 mean mammal capture rate on successive days in Elliot traps Traps run for 7 consecutive nights A total of 185 small mammal captures Quite variable but trend is opposite to that of pit traps with increased capture rates over successive nights mean captures 12 1 8 6 4 2 1 2 3 4 5 6 7 day
Mammalian considerations D. hallucatus monitoring Individual and total captures of quolls with different trap numbers Mean Maximum Linear distance (m) 2 15 1 5 individuals total captures 5 4 25 25 25 2 2 2 15 1 1 individuals 1 1 1 5 5 Meters 9 8 7 6 5 4 3 2 1 Female Sex Male
Mammalian considerations non invasive methods Cameras Searching for sign Hair tubes (targeted) Sand pad surveys (difficult to identify many species reliably) Spotlighting/ head torching Incidental records
Summary of selected methodology Seasonality and weather conditions Trap type Distances between pits Number of successive days of trapping Number of traps per site and in array Type of design dependant on environment and target group(s) Assumptions about traps Supplementary methods but suffer in terms of quantifiable data
Ethical considerations Trap deaths and or injuries Exposure to heat or cold Predation or attack by other animals Physical injury resulting from the trapping Handling Trap hygiene
Ethical considerations Environmental exposure 5 45 4 35 Temperature O C 3 25 2 15 1 5 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 17 18 19 2 21 22 23 Hours Ambient Bucket Covered Bucket PVC Funnel Elliot Covered Elliot
Analysis adequacy of sampling 5% of the total species number caught after 13 individuals and 2 days 75% of the total species number caught after 437 individuals and 14 days Chao1 and Jacknife 1 estimators close agreement Indicates that by the end of the survey ~ 88% of trappable species caught. M. Cowan unpublished
Analysis assemblages A B 12 species site 1 site 2 site 3 a 11 1 4 1 b 8 1 4 8 c d 5 3 1 2 4 4 Abundance 6 4 site 1 site 2 site 3 e 2 3 4 2 f 1 5 4 C g h 1 1 8 11 4 4 a D b c d Species e f g h site 2 site 1 site 3
Sampling regimes Summary Examination of spatial data Appropriate traps defined in EPA/DPaW guidelines Season and climate are important Buckets out perform other similar traps Long lines and number of pits Sequential days Understanding spatial movement patterns helps with trapping Ethics paramount Determination of sampling adequacy Importance of abundance
4 35 3 Analysis importance of abundance P/A True Abundance rand1 rand2 rand3 rand4 rand5 25 2 15 1 5 2 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 17 18 19 2 21 22 23 24 Group average Resemblance: S17 Bray Curtis similarity Resemblance: S17 Bray Curtis similarity 2D Stress:.1 Similarity 4 4 Similarity 6 P/A rand4 rand2 True Abundance 8 1 P/A True Abundance rand1 rand3 Samples rand5 rand2 rand4 rand3 rand5 rand1
Pit trap methodology Species Accumulation Curves: Buckets vs. PVC pipes An example from 35 days over two years covering spring and autumn in the Goldfields 7 6 Buckets were responsible for 1364 of 228 individual captures, or 64.3%. χ²= 219.21, p <.1 5 Difference between species abundances for Buckets and PVC Pipes using Wilcoxon's matchedpairs test (test statistic 53.5, P<.1). S p ecies 4 3 2 Only one species that was more abundant in pipes was statistically significant N. alexis (χ 2 = 2.22, p<.1) 1 144 288432 576 72864 18 1152 1296 144 1584 1728 1872 216 216 234 2448 2592 2736 Trap Nights 288 324 3168 3312 3456 36 3744 3888 432 4176 432 4464 468 4752 4896 54 PVC Pipe Buckets 5184 5328
Ethical considerations heat risk in pit traps Solar exposure to base of traps (2 L buckets and 25 X 6mm PVC pipe) for Perth Time 18:: 17:3: 17:: 16:3: 16:: 15:3: 15:: 14:3: 14:: 13:3: 13:: 12:3: 12:: 11:3: 11:: 1:3: 1:: 9:3: 9:: 8:3: 8:: 7:3: 7:: 6:3: 6:: 5:3: 5:: Time of exposure Base of trap receives no direct exposure Time of exposure PVC pipe bucket Sunrise Maximu m height Month
Reptiles Analysis sampling adequacy Trip 1 Trip 1+2 Trip 1+2+ 3 Trip 1+2+3+4 Trip 1+2.82 Trip 1+2+3.79.97 Trip 1+2+3+4.8.96.98 Trip 1+2+3+4+5.79.92.95.97 Mammals Trip 1 Trip 1+2 Trip 1+2+ 3 Trip 1+2+3+4 Trip 1+2.67 Trip 1+2+3.5.71 Trip 1+2+3+4.59.74.98 Trip 1+2+3+4+5.54.76.92.92
General considerations seasonal variation is species richness 6 Reptiles Mammals 5 4 3 2 1 Autumn2 Spring2 Autumn3 Winter3 Spring3 Autumn4 Winter4 Spring4 Summer5 Autumn5 Winter5 Spring5 Autumn6 Winter6 Spring6 Autumn7 Winter7 Spring7 Autumn8 Species Richness Season M. Cowan unpublished
Autumn2 Spring2 Autumn3 Spring3 Autumn4 Spring4 Summer5 Autumn5 Spring5 Autumn6 Spring6 Autumn7 Spring7 Autumn8 3 2 1 Morethia ruficauda Site 8 Site 7 M. Cowan unpublished
Autumn2 Spring2 Autumn3 Spring3 Autumn4 Spring4 Summer5 Autumn5 Spring5 Autumn6 Spring6 Autumn7 Spring7 Autumn8 3 25 2 15 1 5 Pseudomys desertor All sites M. Cowan unpublished
Other techniques 2m 6m 2m Camera Trap (x 4) 25m Acoustic recorder (x 1) 5m Pit and Funnel drift line (x 2) 25m Type A Elliot Trap (x 2)
Similarity between 1:1, map sheets for all sheets with above mean richness (based on WAM records up to January 24) M. Cowan unpublished