[CINC] 2009 Fox Numbers from Miguel and Rosa

[Mary_C_Fritzsche at nps.gov]

FROM TIM COONAN AT CINP:

Hey I wanted to pass on some good news - and you've all pretty much had a
hand in this over the past decade: our island fox numbers look good. Our
crew (Angela, Jen, Helen, Donivan, Jim, and Sara and Lisa) did a great job
running our fox grids this summer. We ran the numbers recently and came up
with an estimate of 318 for San Miguel and close to 389 for Santa Rosa
(when you include this year's pups in the counts). With the high annual
survival we've had in the past few years (80-90%), this puts us close to
achieving recovery criteria for both islands (the criteria are combinations
of population size and survival that make it unlikely each population will
go extinct in the long run).

We'll keep monitoring, of course, to ensure were on a trajectory for
recovery, and one of these years we'll ask FWS to de-list foxes, based on
the numbers.

Thanks for all the support over the years, truly a group effort.

Tim

----- Forwarded by Kate Faulkner/CHIS/NPS on 10/14/2009 04:50 PM -----
                                                                           
             Tim                                                           
             Coonan/CHIS/NPS                                               
                                                                        To 
             10/07/2009 01:30                                              
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                                                                   Subject 
                                       2009 Fox Numbers from Miguel and    
                                       Rosa                                
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           



Hey, we've worked up the numbers from this year's fox population monitoring
and I wanted to pass them along. It's all good news. For details you can
look at the attached table, but the bottom line is we've got over 300 foxes
on Miguel and close to 400 on Rosa. Which is great, considering that less
than 10 years ago we had 15 on each island, all in captivity.

On Rosa we switched from transects to ladder grids this year so we could
estimate density. We ran 18 2 X 6 grids. Running the data through program
Density, with much guidance from Vicki Bakker, gave us a relatively low
density (0.86 per sq km) that when applied to the island's size (216 sq km)
gives us an adult population size of 187. When we include pups in the
analysis, estimated population size is close to 400 foxes. The confidence
intervals are reasonable, and the coefficient of variation is less than
20%, which is what we're shooting for. This is a marked improvement from
the transect methods we employed last year. We did not estimate density
from that transect data (problematic) but got  a 2008 minimum number known
to be alive of 125. This year it's a bigger number, and a better estimate.

On Miguel our four small (3 x 6) grids continue to get the job done. Adult
density was 6.6 foxes per sq km, which puts it in the mid to upper density
range, compared to the high densities we had in the early 90s. Estimated
islandwide adult population is 256, up from last year's 171 (lambda, or
annual rate of increase, is 1.5, nice and high).

Interestingly, the reproductive effort this year was relatively less than
last year's. This year it was 0.8 pups/female on Miguel and 0.9 pups/female
on Rosa, compared to 1.5 and 1.1, respectively, in 2008. This could be due
to the fact that we're in the third year of a drought (there are low mouse
numbers this fall on Miguel), but also, at least on Miguel, we may be
seeing some declining reproductive effort as populations increase.

Annual survival remains high - above 80% on Rosa and above 90% on Miguel.
We're well on our way to recovery, with no bumps so far.

The fox crew did a GREAT job bringing this data back, especially with the
new challenge of randomly placed ladder grids on Rosa. Thanks, guys!

Tim

|-------------+--------+-----------+-----------+-----+------+--------+-----|
|             | Capture| Individual|    Avg.   |  SE |  N   | 80% CI |  CV |
|             |    s   |     s     |  Density  |     |      |        |     |
|-------------+--------+-----------+-----------+-----+------+--------+-----|
| San Miguel  |        |           |           |     |      |        |     |
|-------------+--------+-----------+-----------+-----+------+--------+-----|
| Adults      |  114   |     64    |    6.64   | 0.98| 256  |207-304 | 14.8|
|-------------+--------+-----------+-----------+-----+------+--------+-----|
| Pups        |  176   |     79    |    8.23   | 1.03| 318  |267-368 | 12.5|
| Included    |        |           |           |     |      |        |     |
|-------------+--------+-----------+-----------+-----+------+--------+-----|
| Santa Rosa  |        |           |           |     |      |        |     |
|-------------+--------+-----------+-----------+-----+------+--------+-----|
| Adults      |  111   |     59    |    0.86   | 0.17| 187  |140-233 | 19.5|
|-------------+--------+-----------+-----------+-----+------+--------+-----|
| Pups        |  148   |     85    |    1.8    | 0.27| 389  |313-466 | 15.4|
| Included    |        |           |           |     |      |        |     |
|-------------+--------+-----------+-----------+-----+------+--------+-----|