Annual Monitoring Project Annual... · 2018-09-23 · ANNUAL MONITORING PROJECT SUMMARY 2018 Save...

Save the Tasmanian Devil Program

Department of Primary Industries Parks Water and Environment

Annual Monitoring

Project 2018 SUMMARY REPORT

ANNUAL MONITORING PROJECT SUMMARY 2018



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Contents

1. Overview.......................................................................................................................................... 1

2. Site descriptions .......................................................................................................................... 3

3. Methodology................................................................................................................................ 5

4. Results ............................................................................................................................................. 7

4.1 Population analysis ............................................................................................................... 7

4.2 Age structure ......................................................................................................................... 9

4.3 Devil Facial Tumour Disease (DFTD) ............................................................................. 12

4.4 Sex ratio ................................................................................................................................. 14

4.5 Breeding females ................................................................................................................ 15

4.6 By-catch ................................................................................................................................. 18

5. Summary ...................................................................................................................................... 19




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1. Overview

Annual monitoring forms core work conducted as part of the Save the Tasmanian Devil

Program (STDP), and is undertaken with funding support from Toledo Zoo (Ohio, US),

one of the Tasmanian Devil Ambassador Program partners.

The aim of annual monitoring is to look at population and disease trends in selected sites

across Tasmania. Annual monitoring first commenced in 2014 when eight sites, each of

which had some previous history of devil monitoring, were selected for annual population

monitoring. The selected sites cover a spectrum of devil facial tumour disease (DFTD)

history, including long-term diseased sites (Buckland and Kempton), sites where DFTD is

newly detected (Granville Harbour), and sites where DFTD is yet to be detected

(Woolnorth).

This year, is the fifth year of annual, standardized surveying of the selected sites and

consistent with previous years, trapping began at Narawntapu National Park in April, and

concluded with Woolnorth in July-August. The timing of trips is shown in Table 1. Each

site is trapped according to standardized protocols, allowing trends in population size,

demographics (age structure, sex ratios, fecundity) and DFTD prevalence to be identified.

Table 1. Dates of 2018 Annual Monitoring surveys

Population and density data from the annual monitoring sites, including data from the

2014-17 surveys, have recently been analysed and published1, highlighting the decline,

but persistence, of populations affected by DFTD.

While the primary aim of annual Tasmanian devil monitoring is to gather information

about population demographics, it also provides an ideal opportunity for collecting

1 Lazenby, B.T., Tobler, M.W., Brown, W.E., Hawkins, C.E., Hocking, G.J., Hume, F., Huxtable, S., Iles, P., Jones, M.E., Lawrence, C. and Thalmann, S., 2018. Density trends and demographic signals uncover the long‐term impact of transmissible cancer in Tasmanian devils. Journal of Applied Ecology, 55(3), pp.1368-1379.

Site Dates of survey

Narawntapu April 11 – April 18

Kempton May 16 – May23

Fentonbury May 16 – May 23

Granville May 23 – May 30

Bronte May 30 – June 5

Buckland July 4 – July 11

Woolnorth July 25 – August 1




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biological samples such as ear and tumour biopsies, blood and faecal samples from

around the State. These samples are used by the STDP and various collaborators to

undertake research associated with DFTD evolution, the response of devils to DFTD, devil

genetics, and other specific questions.

In 2018, samples were specifically collected for research being undertaken by scientists at

the University of Cambridge (UK) associated with DFTD, and for research associated with

analysis of devil endoparasites and ongoing investigation of devil genetics undertaken by

scientists with the University of Sydney.

Monitoring the eight sites for seven nights each, is a big undertaking that couldn’t be

achieved without the valuable assistance of many people, from volunteers and interns

who help out in the field, to landowners who kindly allow access to their properties, to

accommodation owners who provided warmth and comfort after a long day trapping.

The financial support of Toledo Zoo is also specifically, gratefully acknowledged.

Staff:

Sam Fox, Jodie Elmer, Clare Lawrence, Bill Brown, Billie Lazenby, Phil Wise, Carly Lambert,

Dom del Veccio, Drew Lee

Interns and volunteers:

Jasmine Sillince, Natasha Szybinski, Emma Dale, Neville Lazenby, Maya Rasmussen,

Christina Davidsen, Laura Sherman-Hayes, Heather Janetski

Landholders:

Forico, Sustainable Timber Tasmania; Royce Smith (Granville Farm); Tasmanian Land

Conservancy; Australian Defence Force; Van Diemens Land Co.; Woolnorth Wind Farm

Holdings; Parks and Wildlife Service, DPIPWE; Steven and Shelley Chaffey; Gerald and Sue

Ellis




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2. Site descriptions

The eight annual monitoring sites surveyed by the STDP are shown in Figure 1. Four of

the sites can be considered long-term diseased, with DFTD having been present for at

least 10 years prior to the first annual monitoring surveys in 2014. The Narawntapu and

Takone populations have more recent histories of DFTD, while DFTD was first detected at

Granville Harbour during the 2015 annual monitoring survey. DFTD has not been detected

at Woolnorth, in the far north-west to date, although potential DFTD was found by other

researchers working just east of the site earlier in the year.

The sites include managed forests (Takone, Kempton, Bronte Park and Buckland); forested

conservation (Bronte Park), and farmland/open grassland (Fentonbury, Granville,

Woolnorth). All sites have at least some patches of native forest or scrub and within each

site, traps are positioned across a range of habitat types.

The Narawntapu devil population was augmented in September 2015, with 20 captive-

born devils released inside the park. Although it is likely that most of these released

animals have perished, one of the males was trapped during the 2018 survey. The

Buckland population was augmented in June 2018 (just two weeks prior to the Annual

Monitoring survey) with 14 devils from Maria Island. Seven of the 22 devils trapped during

the survey were from this group. The data presented here excludes the released animals

trapped during the survey (i.e. age and sex structure and disease prevalence are

calculated from the 15 ‘incumbents’ only), but it is highly possible that the presence of

the released animals may have influenced the trapability of the incumbents.

Consequently, comparisons of the 2018 Buckland survey against previous surveys at the

site should be treated with caution.




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Figure 1. The eight STDP Annual Monitoring sites, with the year in which DFTD was

detected at each site




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3. Methodology

All trapping trips are run in accordance with Save the Tasmanian Devil Program’s

Standard Operating Procedures (SOPs) for trapping, handling and sampling wild devils.

For each survey, 40 PVC pipe traps (Figure 2) are deployed for seven nights across an

area of approximately 25 sq km. Traps are positioned so they are level, sheltered, and

safe from flooding or rolling. Where possible, the same trap locations are used across

years, but this is not always feasible due to changes in vegetation or access, or if there is

evidence that traps are not safe for any reason. If a trap has to be moved, it is repositioned

within the existing ‘footprint’ of the site, ideally as close to the original location as possible.

The traps are baited with lamb for consistency, and to avoid contaminating scats if dietary

analysis is to be undertaken. No additional lures are used.

All traps are checked daily. If a target species has been trapped (devil, eastern quoll or

spotted-tailed quoll), it is tipped into a hessian sack and scanned for a microchip. After

the first couple of days, devils can be scanned in the trap—i.e., without being bagged—

so those already trapped and processed on the trip can be released immediately. If a

devil is yet to be assessed, it is microchipped (if not done on previous trips), and two or

three small biopsies are taken from the edge of the ear for genetic analysis.

The devil is then assessed for age, the presence of lumps or lesions consistent with DFTD,

and body condition. Age (to one-year cohorts) is determined through a combination of

molar appearance and the growth of the upper canines. Other morphometric

measurements (weight, head width), observations of behaviour and pouch appearance

(where relevant) are recorded for each individual.

If DFTD is suspected, lesions are biopsied and samples are sent to Mount Pleasant

Laboratories for histological diagnosis. Additional tumour samples are only collected if

required to do so to assist researchers undertaking specific research projects, in

accordance with prior agreement and as per Animal Ethics approval. Not all suspected

tumours can be sampled: some are in places that are deemed unsafe to biopsy (e.g. inside

the mouth) and no more than three lesions are sampled per devil (unless the devil has

been euthanased for welfare considerations). Consequently, not all devils assumed to be

infected with DFTD can be histologically confirmed to be so.

Once all data and samples have been collected, the animal is released from the sack. If

the devil is in very poor condition and euthanasia is deemed necessary, the animal will be

placed into a clean trap and transported to the nearest veterinary clinic.

Once the animal has been removed, the trap is thoroughly cleaned and disinfected,

rebaited and re-set. If a quoll is trapped, it is weighed and microchipped if not previously

done, and the sex and reproductive status (if female) are determined.




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Since 2015, the Takone site has been surveyed by the University of Tasmania (Utas). To

minimise the impact of frequent trapping on the devils in this population, the Save the

Tasmanian Devil Program has used the Utas data from Takone for the 2015-2018 surveys.

Trapping is conducted according to similar protocols as the other sites, but traps are set

over ten nights. Consequently, the 2014 data from Takone (STDP, seven nights) is not

directly comparable with the 2015-18 data and is excluded from the results presented

here.

Figure 2. PVC pipe trap in situ




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4. Results

4.1 Population analysis

An estimate of the population size for each site in each year is determined through

capture-mark-recapture (CMR) analysis. Data from each survey is analysed in MARK

(model: closed capture P and C full likelihood population estimate, CHAO (M(th)) which

incorporates heterogeneity in individual trapability and capture likelihood across survey

nights.

Survey results from 2014 to 2018 show different apparent trends in population numbers

across sites (Figure 3). Kempton and Bronte are showing apparent zero-growth

population trends across the five years of Annual Monitoring surveys. The Buckland

population (graphed with the recently released devils excluded from the analysis) has also

shown no obvious positive or negative trend, but an increase in future years would be

expected.

DFTD was first detected at Granville Harbour in 2015; since then, there has been a slight

apparent decrease in the estimated population size, but this may be an artefact of a

particularly high estimate in 2015, because the estimates remain within the range of

previous years. It is anticipated that a decline will be seen in the next few years as a result

of disease presence.

As was expected, the Narawntapu population has increased slightly following the release

of devils into the park in late 2015, with population estimates increasing by 35% between

2016 and 2017, and by 25% between 2017 and 2018.

The Woolnorth population is showing no evidence of decline despite low breeding rates

at the site (see section 4.5).

The Takone population has shown a steady decline since 2014 (Figure 3), with only 23

animals trapped in 2018 compared to a high of 69 in 2015. In 2014, DFTD had been present

at the site for approximately four years. Previously, the decline in devils at Takone was

partially attributed to large-scale land clearance within the site in 2015; however, the

continued decline, along with the absence of a similar pattern following land clearing at

Kempton in late 2016, is evidence that other factors (including DFTD) are likely involved.

In contrast to Takone, the Fentonbury population has shown a steady increase over the

five years of annual monitoring (Figure 3). While there is no clear explanation for this

trend, it is reinforced by additional longer-term population analyses conducted by the

STDP and collaborators.




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Figure 3. Population estimates for the eight Annual Monitoring sites based on capture-

mark-recapture analysis. Dots represent mean estimate, vertical bars represent the range

between upper and lower 95% confidence intervals. Note the different y-axis scale for

Woolnorth. The 2014 data from Takone have been excluded as they are not directly

comparable with later years.




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4.2 Age structure

As expected, young (first- and second-year) animals constitute a high proportion of the

devils trapped in medium and long-term diseased sites, with few older animals present

in these populations (Figures 4 and 6). Interestingly, in 2018 an unusual number of older

animals were trapped, including the first 4-year-olds trapped at Bronte (n = 1) and

Fentonbury (n = 2) since the start of the annual monitoring surveys in 2014. Healthy

(DFTD-free) five-year-old animals were trapped at Kempton (n = 2), Narawntapu (n = 1),

Takone (n = 1) and Granville (n = 1). A highlight of the Narawntapu survey was the capture

of seven-year-old ‘Boots’, who was released into the park in 2015 and remains free from

DFTD.

Until this year, Takone has retained an age structure broadly similar to that of non-

diseased or early-diseased sites (eg. Granville and Woolnorth, see Figure 4). More than

half (6/11) of the two-year-old devils trapped at Takone in 2017 had DFTD in that year,

suggesting a low proportion of this cohort would survive to 2018. This year, accordingly,

the site showed an age structure more similar to other diseased sites (Figure 6), with a

heavy predominance of one- and two-year-old animals and just a single older animal.

This pattern is likely to continue, given five of the eight two-year-old animals trapped in

2018 were found to have DFTD.

The Buckland population was augmented with eight 2-year-old animals, nine 3-year-old

animals and seven 4-year-old animals, just prior to the 2018 survey. Figure 6 shows the

age structure of devils trapped at Buckland with and without the release animals included

(seven release animals were trapped during the survey). It is worth noting that footage

from remote cameras set up around the site during and after the release at Buckland

suggests some older animals are present at the site but are not going into traps (Figure

5).




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Figure 4. Age structure of Annual Monitoring sites, calculated as the average proportion

of devils in each cohort across five years of survey. The left-hand sites (Bronte, Buckland,

Fentonbury, Kempton and Narawntapu) have had DFTD for 10+ years; Takone for 8 years;

Granville for 3 years; and Woolnorth remains disease-free.

Figure 5. Old, possibly diseased devil captured on camera at Buckland but not trapped

during annual monitoring survey.




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Figure 6. Proportion of trapped devils in each age cohort, in each year of survey. Buckland

data are shown with trapped release animals excluded (‘Buckland’) and included

(‘Buckland_release’). The 2014 data from Takone have been excluded as they are not

directly comparable with later years.




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4.3 Devil Facial Tumour Disease (DFTD)

While it is impossible to conclusively diagnose DFTD in the field, we can use characteristic

features (appearance and feel) to assess how likely it is that a lump or lesion is DFTD. All

trapped devils are given a ‘DFTG’ score, which represents the likelihood that the devil has

DFTD based on gross physical examination. Scores range from 1 (no signs of DFTD-like

lesions with full examination of the animal) to 5 ( presence of lesions highly suggestive of

DFTD, as in Figure 7).

The prevalence of DFTD in each population was calculated as the proportion of all

captured individuals who were given a DFTG score of 5. It is important to note that not

all of the animals given a DFTG score of 5 have been confirmed as having DFTD; similarly,

it is possible that some animals given a lower DFTG score may have had DFTD. As DFTD

is relatively uncommon in one-year-old devils, Figure 8 presents the proportion of (i) all

captured devils, and (ii) only devils aged 2 years or older, showing evidence of DFTD.

Disease prevalence at Granville remains low, three years after DFTD was first detected at

the site. No evidence of DFTD was detected at Woolnorth, although earlier in the year

other researchers had found devils with lesions consistent with DFTD at Robbins Island,

less than 30km from the Woolnorth site.

A three-year-old male from Bronte, ‘Captain Thunderpants’, showed evidence of tumour

regression. He was trapped in 2017 with a lesion subsequently confirmed as DFTD, but

showed no evidence of this or any other lesion when trapped in 2018. The ability to follow

individual animals over time, and identify cases like this, is one of the major benefits of

the annual monitoring work.

Figure 7. Different presentations of DFTD, scored DFTG 5, on Maleficent (Narawntapu,

left) and Bagel (Kempton, right)




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Figure 8. Proportion of trapped devils showing gross evidence of DFTD. Note this is from

examination in the field only, some cases have not have been histologically confirmed as

DFTD. No devils with DFTD have been detected at Woolnorth. The 2014 data from Takone

have been excluded as they are not directly comparable with later years.




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4.4 Sex ratio

The ratio of males to females trapped remains fairly even in all sites (Figure 9). Some

fluctuations are apparent among years, but this is most likely an artefact of small sample

sizes. Woolnorth, with by far the highest number of captures (110 individual devils in 2018),

has shown a slight male bias over the last two years.

Figure 9. Sex ratio of trapped devils across survey sites. The 2014 data from Takone have

been excluded as they are not directly comparable with later years.




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4.5 Breeding females

The proportion of trapped females showing signs of breeding (eg. pouch young [see

image below] or lactating teats) varies considerably across years within each site (Figure

10). The 2018 data for Bronte, Granville, Narawntapu and Kempton are more or less

consistent with previous surveys. Breeding rates at Takone appear to be decreasing as

the population declines, possibly because of the loss of older, breeding-age females.

Observed female breeding rates were low at Buckland, possibly because of the small

number of 2+ year old females trapped (Figure 10 shows Buckland data with the release

devils excluded). Breeding rates appear to have declined at Fentonbury over the last three

years.

The proportion of females breeding at Woolnorth has been notably low across the five

seasons of annual monitoring. A recent University of Sydney analysis using annual

monitoring data from 2014-162 showed a significant decline in breeding rates at

Woolnorth compared to earlier surveys of the site (2004-2009). Over the past five years,

there has been a slight increase in the proportion of females breeding (linear regression,

all females included: = 0.033 P = 0.014, Figure 10; linear regression, one-year-old

females excluded: = 0.046, P = 0.068).

Image: C. Lambert

2 Farquharson, K.A., Gooley, R.M., Fox, S., Huxtable, S.J., Belov, K., Pemberton, D., Hogg, C.J. and

Grueber, C.E., 2018. Are any populations ‘safe’? Unexpected reproductive decline in a population of Tasmanian devils free of devil facial tumour disease. Wildlife Research, 45(1), pp.31-37.




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Figure 10. Proportion of all trapped females showing evidence of breeding (pouch young

or lactating teats). The 2014 data from Takone have been excluded as they are not directly

comparable with later years.




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The prevalence of precocial breeding (breeding at one year of age) varies across sites.

No precocial breeding has been detected at Granville or Takone across the five years of

the project, although more than half of one-year-old females at these sites are at a pro-

oestrus stage (having a characteristic oily red exudate in the pouch) at the time of capture.

Figure 11 shows the proportion of one-year-old females showing signs of having

completed at least one oestrus cycle by the time of capture, as evidenced by (i) pouch

appearance consistent with post-ovulation, (ii) pouch young, or (iii) lactating teats

(denned young). When females in pro-oestrus are included in the data from Figure 11,

the proportion of one-year-olds that are sexually mature at the time of capture ranges

from 75-100% within each year. Figure 11 shows considerable variability across and within

sites, but in many cases this is likely to reflect small samples sizes: for instance, at Buckland

in 2015 and 2016, only two one-year-old females were trapped. Precocial breeding is

infrequent but does occur at Woolnorth, suggesting that low population density is not

the only driver of early breeding in devils.




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Figure 11. Prevalence of precocial breeding (one-year-old animals with pouch young or

evidence of completed ovulatory cycles) in annual monitoring sites where precocial

breeding has been detected. [Note in some cases sample sizes were very small]

4.6 By-catch

Spotted-tailed quolls were trapped at Bronte (1 individual), Fentonbury (1), Kempton (1),

Narawntapu (10) and Woolnorth (17). No eastern quolls or cats were trapped during the

surveys.




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5. Summary

After five years of annual monitoring surveys, our data shows that most populations are

persisting despite the presence of DFTD. Two of the eight survey sites are showing clear

demographic patterns: at Fentonbury, the population is steadily increasing, and the

proportion of older animals is also showing a slight increase. In contrast, devil numbers

at Takone are declining, and the age structure is becoming more like that of a ‘typical’

diseased site. Otherwise, patterns in population size estimates (Figure 3), disease

prevalence (Figure 8), age and sex structure (Figures 6 and 9) and fecundity (Figure 10)

vary across sites and years, regardless of how long DFTD has been present in the

population. Observed annual fluctuations are likely due to a combination of small sample

sizes (in many cases) and stochastic or environmental factors. This highlights the

importance of long-term data collection, a key aim of annual monitoring, for robust

identification of population trends. As the two publications cited in this report attest, data

collected during annual monitoring surveys are becoming increasingly valuable for the

STDP and its collaborators as the duration of the monitoring surveys increases.

Notable in 2018 were a number of older, healthy devils trapped in diseased sites.

Hopefully, samples collected from these animals can help researchers determine whether

genetics influence the likelihood that a given devil will develop DFTD.

GPO Box 44, Hobart TAS 7001

Email: [email protected]

Visit: www.dpipwe.tas.gov.au

Annual Monitoring Project Annual... · 2018-09-23 · ANNUAL MONITORING PROJECT SUMMARY 2018 Save...

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