Thursday, April 30, 2020

Arrival of Juvenile Leopard Frogs

juvenile Leopard Frog, Canada: Quebec:
St-Barthelemy boatlaunch, in backwater of Maskinonge River,
at its mouth on the St Lawrence River, 9.88 km SSW Maskinonge.
(107m btwn wpts), 31I/3, 46.14849° N 73.07223° W
Arrival and abundance of Juvenile Leopard Frogs in Bishops Mills

citation of truncated version: Frederick Schueler. 2019. Arrival and abundance of Juvenile Leopard Frogs in Bishops Mills.CHORUS: Newsletter of the Ottawa Amphibian and Reptile Association 35(7):4-6

There’s a verse in the Leopard Frog song that goes – 

Let us live here in Bishops Mills
On the first of every August
When the metamorphs from the South Branch marsh
Come and fill the fields and the gardens.

- but this year the first juvenile Lithobates pipiens didn’t show up until the 17th of August, which has inspired me to see how variable the date of arrival has been by filtering our database with - RTOD(ACOS(COS(DTOR(LATITUDE-44.87246))*COS(DTOR(LONGITUDE--75.70096)*COS(DTOR(44.87246)))))*111.2<=[x].AND.NAME="Rana pipiens".AND."juv"$LIFE_STAGE.AND.BETWEEN(MO,7,8) – i.e., juvenile Leopard Frogs within [x] kilometres of the central intersection of Bishops Mills during July & August. This was run twice, for a 500m radius and a 200m radius.

I wrote to the NatureList on 13 August 2001:  “The first of August is the traditional date for the arrival of the first juvenile Leopard Frogs at our place. With the drought this year, the little frogs transformed in mid-July, but they've been restricted to the banks of waterbodies, where they serve as victuals for Bull Frogs and various Birds (it's a great year to be a juvenile Heron).”
There are several classes of years here: 1979-1990 when notes were all on paper and most local records were not transcribed when records were gotten out for the Ontario Herpetofaunal Summary, 1990-2003 when many records were loaded into the database, and 2004 to present when there were (when we were home), systematic surveys of the 267 m of streets that bordered land we have owned in the village (Schueler, Frederick W. 2007. Doing the Streets: Animals on the Road in a Rural Ontario Village, 2004-2006. Roads & Ecopassages Forum, 20-22 March 2007, Toronto Zoo.

There have also been years, such as 1985-1986, 1988-1989, 1990, 1994, & 2014-2015 when we were away from home in the field during the arrival season. Since 2010 the New Brunswick Museum Protected Natural Areas biotic surveys (called by their current name of BiotaNB in the table), have mandated 3-week departures from home in August in alternate years. This has usually been after the first arrival, but meant we didn’t have a first arrival date in a couple of years. 

In the 23 years of data,  the mean first record is 31 July, for the 500m radius, and 1 August for the 200 m radius, ranging over more than a month from 18 July – 26 August, with a standard deviation of 9.36 days, nicely confirming our intuitive estimate of arrival on the first day of August. There is no striking secular trend in the dates, with both early and late arrivals recorded early and late in the sequence. 

I asked Justin Robert of the Rideau Valley Conservation Authority about historic drought/low water records, and he replied: "As for the low water declarations, it has actually proven quite challenging to find a consistent record of past submissions... I made a request to the MNRF for their records of past declarations as they track low water conditions throughout the province based on the submissions of the conservation authorities," and they sent a spreadsheet of all low water announcements since 2000 as a colourfully-coded spreadsheet  (e-mail, 23 Aug 2019). Justin extracted the RVCA row of this and provided the summaries for the low water years since 2000 in Table 1 (and remembering 1999 as a severe drought year, even though it’s not in the table). 

In the nine years when some low water or drought was reported before August the mean arrival date was 2 August, and if the two years when this low water occurred only before June were excluded, the mean arrival date was 6 August, confirming our impression that drought delays the arrival of the frogs, presumably because small frogs would move less rapidly across a dry countryside.

The most anomalous year was 2013 when the first record was 26 August with only 2 records of 2 frogs, which was 5% of 85 on-road records (we were home from mid-July on). After the 2012 drought, there had been “Level 1” low water in January & February, and this may have led to mortalities in the creek,. The frogs in the “remote aquatic hibernaculum” (=roadside ditch) that I monitor in the village were all killed when it froze solid.  The 7 August arrival in the wet summer of 2017 (5 records, 6 frogs -- 6% of 106 on-road records), may also reflect a decreased breeding population after the drought year of 2016. 

In July & August 2002 we recorded 262 Leopard Frogs, in 2004 97 frogs, in 2005, 112 frogs, in 2008,  254, and in 2011, 118. Since then we haven't had more than 18 frogs in any July-August period. These were the years when we also had a resurgence in Chorus Frog calling, which we attributed to "years of wet summers, when dispersal to new sites would be possible" (Schueler & Karstad. 2013. Preliminary Results: Do dry springs and moist Augusts favour Chorus Frogs in Bishops Mills, Ontario? CARCNET, Orford, Quebec, Sept 13-16 2013). It seems that to build up a big population of Leopard Frogs takes two successive years of favourable weather, but a full treatment of the situation will require detailed weather & stream-flow data, transcription of  notes from the 1980s & 1990s, a full analysis of when we were present to observe arriving juveniles, and consideration of our other data on calling, winter mortality, and movements in other seasons.

Take me down onto Cooper Road
In the first week of December
When the cold rain falls on the last to go
To some hole that stays unfrozen.

Table 1. First Arrival of Juvenile Leopard Frogs (Lithobates pipiens) in Bishops Mills, Ontario, 1991-2019

For each year this lists the first day when a juvenile frog was recorded within 500 m of the central intersection of the village (44.87246° N 75.70096° W, WGS 84 datum), and if this was more than 200 m from the intersection, the date a juvenile was found within 200 m, the number of records mentioning juveniles and the number of frogs (of any age) in those (500 m) samples, from 2000 on the months when there were drought or low water advisories, from 2002 on the number & percentage of the streets survey species records the juvenile Leopard records comprise, and from 2009 on the date we left for August BiotaNB surveys, usually for the rest of the month. All records are in the Ontario Reptile & Amphibian Atlas.

22 July 1991 – 2 records, 8 frogs

29 July 1993 – 3 records, 37 frogs

1994 (not at home during the arrival season)   1 record, 4 frogs

22 July 1995 – 4 records, 49 frogs

1 August 1996 – 2 records, 8 frogs

16 August 1997  –  1 record, 1 frog

2 August 1998 – 2 records, 4 frogs

5 August 1999 – 1 record, 1 frog – a severe drought year

26 July 2000 – 4 records, 27 frogs

13 August 2001 –  2 records, 3 frogs – April-June, Level 1 low water

28 July 2002 – 14 records, 262 frogs – 64% of 14 on-road records (28 July SSE of village, first in village 29 July)

1 August 2003 –  8 records, 37 frogs – 29% of 17 on-road records.  August, Level 1 low water

27 July 2004 – 23 records, 97 frogs – 29% of 78 on-road records (27 & 31 July, 2 records outside of village, first in village on 1 Aug.)

26 July 2005 – 24 records 112 frogs – 27% of 110 on-road records.  (26 July, SE of village, first in village on 27 July – at arrival "Conditions have been optimal for them all year.") –  August-December, Level 2 drought

30 July 2006 –  4 records 34 frogs – 33% of 15 on-road records.

9 August 2007 – 6 records 8 frogs – 12% of 123 on-road records.  June-July, Level 1 low water

25 July 2008 – 35 records, 254 frogs – 21% of 151 on-road records.

29 July 2009 -15 records 24 frogs – 8% of 208 on-road records. (left for BiotaNB on 9 Aug).

24 July 2010 – 10 records, 27 frogs – 13% of 70 on-road records.   January-July, Level 1 low water (left for BiotaNB on 9 Aug).

20 July 2011 – 29 records, 118 frogs – 19% of 173 on-road records.  – August-January 2012 – Level 1 low water

4 August 2012 – 4 records, 6 frogs – 5% of 97 on-road records. – March-October, Level 3 drought. The curse – “May the vehicles of all nonherpetologists find their gas tanks infused with sugar.” – appears in the notes. (left for BiotaNB on 10 Aug).

26 August 2013 – 2 records, 2 frogs – 5% of 85 on-road records. – January-February, Level 1 low water – home from mid-July on.

2014  (left for BiotaNB on 3 August)  0% of 32 on-road records.  This was after a winter of extreme anoxia and frog mortality in the creek.

2015  (not at home during the arrival season)  0% of 11 on-road records.   – March-June, Level 1 low water

18 July 2016 – 12 records, 18 frogs – 11% of 84 on-road records –  May 2016-April 2017, Level 3 drought (left for BiotaNB on 9 Aug).

7 August 2017 –  5 records, 6 frogs – 6% of 106 on-road records.  

25 July 2018 – 14 records, 16 frogs – 10% of 145 on-road records. –  July-November, Level 3 drought

17 August 2019 – 4 records, 4 frogs – 4% of 113 on-road records –  August-September, Level 1 low water

Bishops Mills bridge, over the creek that provides breeding and hibernation
sites for the population. The bridge is beyond the 200 metre radius,
but within the 500 metre radius of the arrival summaries.
Fred Schueler. 2019. Jennifer's Curriculum of Seasonal Metapopulation Dynamics of Rana pipiens in Eastern Ontario..CHORUS: Newsletter of the Ottawa Amphibian and Reptile Association 35(7):7-8.

 (from her father on her 16th birthday, 13 May 2002, ‘Damsel frogs’ verse October 2019 - first year females moving to feed separately from the breeding migration.“Sewage traffic” is the population growth of Kemptville brought on by the construction of a new sewage treatment plant and construction of Highway 416.“Take me...” verses were situations we’d been in together.“Come with me...” were places she hadn’t been.“We’ll go...” was a situation I’d heard of but neither of us had been to.)

Take me out onto Middle Creek
When the channel has refrozen
And the February sunshine gleams
Over sleepers on the bottom.

I’ll be there at Scotts’ dugout pond
When the ice is just retreating,
And the sun-warmed banks are thronged with those 
Who know that spring has broken.

Take me out onto Clothier Street -
Midnight on the first of April -
When North Grenville’s urban core becomes
A migratory venue.

Come with me to the Rocksprings Road,
About four clicks north of Greenbush,
When the night is filled with the rolling snores
Of a full motorboat chorus.

An Anuran tide arising.

(Keep me far from the Kemptville Mall
and the jammed up sewage traffic -
from the 416 where Hell’s machines
are popping off the migrants).

Take me out onto the Branch Road
As a hard May drought is watered,
And the damsel frogs flee the foodless shores,
for the fields and their Grasshoppers.

We’ll go up into Gatineau Park
When the Beaver floods are seething
And the Duckweed and detritus boils
With the tadpoles in their thousands.

An Anuran tide arising.

(Keep me far from the tile-drained fields
and the atrazine ammonia
Where the Corn is high, but the dust is dry
and an extra leg is an option).

Let us live here in Bishops Mills
On the first of every August
When the metamorphs from the South Branch marsh
Come and fill the fields and the gardens.

Come with me through September fields
When the twice-cut hay is waving,
And the ova grow, and thumbs start to show,
With Grasshoppers disappearing.

An Anuran tide arising.

(Keep me far from the Fallowfield
and the plastic-covered housing
Where yuppies only are hopping by
and the Jock runs nearly empty).

Walk the banks out at Maplestone
When October leaves are falling, 
And the woods and fields are given up 
In dark longing for the water.

Take me down onto Cooper Road
In the first week of December
When the cold rain falls on the last to go
To some hole that stays unfrozen.

An Anuran tide arising.

(Let us live here in Bishops Mills,
In the Merricksville quadrangle,
In a land that’s shared by man and frog,
Garter Snakes, and Blanding’s Turtles,
with joint sovereignty acknowledged.)

Come with me onto Middle Creek
When the channel has just frozen
And the January sunshine gleams
Over swimmers on the bottom.

An Anuran tide quiescent.

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