Oregon Silverspot Butterfly Field Support for Population Augmentations, Central Oregon Coast

Report to U.S. Fish & Wildlife Service Project Title: Oregon Silverspot Butterfly Field Support for Population Augmentations, Central Oregon Coast

Submitted by: Kaegan Scully-Engelmeyer Private Contractor December 2015

This report reviews and summarizes the fieldwork methods, results and discussion of the 2015 Oregon Silverspot Butterfly (OSB) population augmentations conducted at the Rock Creek, Big Creek, Bray Point, Agate Meadow, and Cascade Head release sites on the Central Oregon coast. The Woodland Park Zoo provided the contract funding for the field support. The releases were implemented in cooperation with the U.S. Department of Fish and Wildlife, the U.S. Forest Service, and the Nature Conservancy. The captive rearing programs at the Oregon Zoo and the Woodland Park Zoo supplied the OSB pupae for the releases.

METHODS

Mimicking the natural OSB life cycle, the Butterfly Labs at the Oregon Zoo and the Woodland Park Zoo simulate the onset of the spring/summer seasons by removing the OSB larvae from the refrigerators in the early spring and consequently inciting the continued development of the butterfly larvae. By mid July the first caterpillars begin to pupate, as they do they are each placed in their own folded paper envelope and put into bead boxes. Each envelope has written on it information about each pupae including its own identification number, rack and bin number in the lab, date pupated and its mother. The bead boxes in which they are placed each have 24 compartments and are accompanied by a data sheet recording the information of all of the pupae. At this point they are ready to be released into the field. Every week The Woodland Park Zoo sends a shipment of their pupae to the Oregon Zoo and from there the Field Support Technician transports them out into the field. This is done on a weekly basis from mid July through the end of August.

This year the pupae were released in six areas: Area 8 of the Rock Creek (RC) site, Bray Point (BP), Cascade Head (CH), Big Creek (BC), and two sections of Agate Meadow (Agate Meadow “AM” and Agate Meadow North “AMN”). The pupae were disproportionately distributed amongst the sites due to a number of factors but mainly because as the season progressed there were a large number of pupa from two very productive mothers (MH-21 and MH-06); as a result, efforts where made to distribute their pupa across more sites to encourage diversity amongst breeding butterflies.

Aside from some small modifications the Pupae were released using the Open Tub Release Method developed during the 2011 release season at Bray Point. The cages were staked down in areas with good sun exposure and an area in the southwest corner of all of the cages was left open. The theory is that the butterflies are attracted to the sun and tend to be more active in the afternoon, thus the afternoon sun in the southwest region draws the butterflies out of the cage. Nectar plants were placed in the opening to further attract the recently eclosed butterflies to the opening (Photos 1 and 2). Mesh tubes were fastened to the small opening of the cages in order to provide protection to the opening from birds entering the cages. This addition was put in place as a response to the bird predation that took place at the AM site in previous seasons.

Inside each cage, plastic tubs were placed upside down with openings cut in the sides. These provided the pupae shelter from the elements. The tubs varied in size, either fitting one or two bead boxes underneath it. Consequently each cage was able to hold either one or two tubs inside. Each cage could hold up to 48 pupae inside at any given time; in total there were 25 cages.

Weekly visits were scheduled for the sites starting in the middle of July and ending in early September. During these visits each pupa in the field was inspected, if the pupa had eclosed, it was recorded using mobile data collection software Liquid (https://getliquid.io) and the pupa paper was removed from the cage. In addition to the weekly visits, a USFS intern working on an OSB monitoring effort in the area provided additional support recording successful releases throughout the week.

Three weeks after the last pupa was released each pupa paper was inspected to determine if the pupa had eclosed. All of the subsequent information was recorded via Liquid and then later exported to excel for review. Due to the nature of the self-release cages, it is assumed that if there was no sign of the butterfly it had successfully eclosed and escaped. Ultimately a pupae paper found empty was marked as “Y” (successful) unless there was evidence of predation in the cage traceable to the pupae; in which case they were marked with a “P-YJ” signifying yellow jacket predation or “P-?” signifying unidentifiable predation. In the case that a pupa was found partially eclosed without any sign of predation it was denoted as “N-P”. Pupa visibly dried out and dead or left over at the end of the season after being out in the field for 2 months were noted as “N” or unsuccessful. RESULTS

Between July 21st and August 11th a total of 1034 OSB captive-reared pupae were released into the field (Figure 1). The deconstruction of the cages and the counting of the pupae began during the final week of August and the last pupae remained in the field until September 10th. 443 pupae were released at the Bray Point (BP) site, 344 at Rock Creek (RC), 140 at Agate Meadow (AM), 21 at Agate Meadow North (AMN), 38 at Big Creek (BC), and 48 at Cascade Head (CH). In addition to the pupae, 21 larvae were released (18 from WPZ and 3 from OZ). In total there were 1034 OSB pupae sent out to the field this year. Of those, 825 were released successfully as adults resulting in a 79% success rate overall, thirteen percent higher success rate than we experienced last year (Figures 2.1, 2.2). Not included in the total of successfully released adults were 26 pupae that partially eclosed but did not survive (N-P), 184 pupae that never eclosed (N), 3 pupae that were lost to yellow jacket predation (P-YJ) and 6 pupae that appeared to have been eaten by an unidentified predator (P-?). All of the OSB released this year originated from the eggs of 24 mothers collected last fall (Table 1).

One of the cages at the Bray Point release site was near a yellow jacket nest and this resulted in the only discernable type of predation seen this season. This was evident because individual butterflies were seen being attacked by yellow jackets and discarded with wings intact but body consumed. After the first sign of this type of predation the cage was closed and the pupa moved resulting in only 3 pupa being lost in this way.

The differences between the zoos success rates are examined in Figures 3.1, 3.2 and 3.3. This year the releases from the Oregon Zoo resulted in slightly less adult butterflies than the Woodland Park Zoo, but both zoos oddly enough had the same number of pupa fail to eclose.

The breakdowns of timing and success across the release sites are shown in Figures 4.1, 4.2. The BP site experienced a significantly higher amount of unsuccessful eclosures (150 out of the 184 total). It also saw a larger portion of the pupa earlier in the season, suggesting weather conditions earlier in the season may have played a part in preventing some of the first pupa from eclosing.

DISCUSSION

During the previous two seasons voles had been the most impactful source of predation during the releases, taking more than 150 pupa last season alone. The frequency of the predation appeared to be increasing over the course of the season, leading to the theory that the voles were especially sensitive to the smell of the meconium remaining on the papers of eclosed butterflies. We then surmised that the voles were attracted to the cages when the papers were left in the bead boxes until the end of the season as we had been doing. This season we removed the used pupa paper once it could be determined that the pupa had eclosed, we did not see any predation of this kind. It is impossible to say definitively that removing the paper throughout the season is connected with the lack of vole predation this year, but regardless it was nice not to lose so many to the voles. I recommend continuing this method of removing the pupa papers as the season progresses just in case it is directly connected.

As was briefly mentioned in the results (and best demonstrated by figure 4.2), the Bray Point release site saw far less survivorship than any of the other sites. It also saw a larger proportion of pupa released in the first half of the season (shown in figure 4.1) receiving pupa only on the first three release dates. In fact for those first three release dates, percentage of successfully emerged adult butterflies (Y/total pupa released) emerging on the site were as follows: 7/21 - 36%, 7/28 - 54%, 8/5 - 90%. As you can see the success rate improves dramatically on the site over the course of the season. This combination of factors raises some questions as to how this early influx of pupa resulted in such poor survivorship for the site. Was it weather related, a site-specific factor, or something else entirely? It is hard to say with any certainty. My best guess is that the drought conditions the Oregon Coast was experiencing throughout July was at least partially responsible for the early depression in successful eclosures.

While the number of pupa released this year was almost 700 less than last year it should be noted that the percentage of overall success of the population augmentations was up 13%. I believe this is due to specific methods and cage placement strategies adopted to curb predation from voles, sparrows, yellow jackets, as well as decrease susceptibility of the cages being damaged by herds of Elk.

ACKNOWLEDGEMENTS

I would like to thank Sean Burns for his help counting and recording pupa success, Mary Scully for her help with fieldwork throughout the season, as well as the other individuals who came out and volunteered their time. I would also like to thank Marty Bray from US Forest Service for his continued help throughout the release season as well as his work on all of the OSB sites, Anne Walker from the US Department of Fish and Wildlife for her guidance on all fieldwork matters, as well as the Oregon Zoo Butterfly Lab and the Woodland Park Zoo Butterfly Lab for their great captive rearing efforts again this year. I would also like to thank the Woodland Park Zoo for funding the field support.

Photo 1: Open cage tub method Photo 2 – Close-up of opening

Table 1: # of pupae Rearing # of pupae # of larvae Mother's # emerged as Zoo released released adults MH-01 OZ 32 23 1 MH-01 WPZ 53 41 1 MH-03 OZ 3 3 MH-03 WPZ 1 1 MH-05 OZ 62 51 1 MH-05 WPZ 76 68 6 MH-06 OZ 130 100 1 MH-06 WPZ 143 115 1 MH-07 OZ 9 8 MH-07 WPZ 7 4 MH-10 OZ 2 1 MH-11 OZ 3 2 MH-11 WPZ 6 6 2 MH-13 OZ 8 6 MH-13 WPZ 2 2 MH-20 WPZ 2 0 MH-21 OZ 219 172 8 MH-21 WPZ 246 199 MH-23 OZ 4 4 MH-23 WPZ 6 5 MH-27 WPZ 2 2 MH-28 OZ 10 5 MH-28 WPZ 5 3 QC OZ 3 3 Unsuccessful Eclosures Recorded W/Out Pupa Paper -10 TOTALS 1034 815 21

Figure 1: Release Dates by Zoo

500 450 400 350 170 300 287 250 WPZ 200 OZ 150 235 100 46 171 50 64 46 0 15 7/21/15 7/28/15 8/5/15 8/11/15

Figure 2.1: Success by Release Dates 500

400 Y

300 P-YJ 313 421 P-? 200 N-P 100 40 N 66 77 51 0 31 10 7/21/15 7/28/15 8/5/15 8/11/15

Y: Yes N: No N-P: Partial Eclosure P-YJ: Yellow Jacket P-?: Unknown Predation Predation

Figure 2.2:

Total Success P-?, 6, 1% N-P, 26,

N, 184, 2%

18% N

N-P P-YJ, 3, 0% P-?

P-YJ Y, 825, 79% Y

Figure 3.1: Zoo Comparison

500 447 450

400 378

350

300

250 OZ WPZ 200

150 92 92 100

50 14 12 5 1 3 0 Y N N-P P-? P-YJ

Figure 3.2: Figure 3.3:

Oregon Zoo Woodland Park Zoo

N N-P N N-P 19% 2% 17% 2% P-? P-? 0% 1% P-YJ 1% Y Y 77% 81%

Figure 4.1: Release sites correlated with release dates

200 176 173 180 157 160 151 140 AM 120 110 AMN 100 BC

80 64 BP 56 60 48 CH 38 40 RC 20 21 20 20 0 7/21/15 7/28/15 8/5/15 8/11/15

AM-Agate Meadow, AMN – Agate Meadow North, BC – Big Creek, BP – Bray Point, CH – Cascade Head, RC – Rock Creek

Figure 4.2: Overall Release Site Success

350 321

300 276

250 N 200 N-P 150 P-? 150 130 P-YJ 100 Y 47 50 33 10 18 12 16 3 5 1 3 0 AM AMN BC BP CH RC