Category Archives: Uncategorized

A new life in the air

Am insect transforming from larva to adult is the epitome of metamorphosis. Here’s a dragonfly that’s just left its larval skin and its life as a nymph behind. It rests whilst its wings expand and harden -a vulnerable time for this ancient creature -its design hasn’t changed for 300 million years when they first appeared. Its a voracious hunter both in the water as a nymph and out as an adult. There’s definitely a sinister predatory look about the nymph case. I wouldn’t want to be a stickleback….

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and here’s a couple we made earlier…..

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Its smaller relative, the damselfly. Lovely electric blue flashes amongst the reeds. By the time I had my camera out, they’d gone. But I managed one half-decent shot of this trio. I’ll work on a better image next season.

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The Water Vole

What a gorgeous creature. Spotted on my first Fen Raft Spider survey by our guiding light Ellen, here it was feeding on frogbit, an aquatic plant that looks like miniature lily-leaves. Its name means “frog bite” for reasons that are not clear to me or an eminent aquatic botanist I asked. Its Latin name reflects its meaning: Hydrocharis morsus-ranae. Morsus = bite, ranae = of a frog. Answers on a postcard please!

This is a European water vole, now a threatened species in this country. Its population has declined by over 90% since the 1960s, largely thanks to a spreading population of the foreign invading predatory American mink but also due to farming and watercourse practices. It’s been protected by the UK government since 2008. Curiously in France, farmers are campaigning against the water vole, which they say is causing crop damage.

SWT is doing its bit for water voles by trapping and destroying mink and creating new wetlands and habitat for them,

Here are some pics of the ravishing rodent

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and a video clip. Apologies to wildlife cameramen everywhere for the quality. This was strictly very impromptu amateur photography on a windy day with no monopod or tripod.

Stonechats, not Whinchats

These little birds provoked much excitement in my walking partner on a fine September morning’s fen raft spider survey. She tends to hit people when excited but I got away lightly and unbruised. The reason for her excitement was thinking we might have seen Whinchats. Close examination of my pics confirmed they are Stonechats. Me, I wouldn’t know the difference if they flew up my nostrils. But this page should help me learn a thing or two.

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Study 1

Fen Raft Spider behavioural study record 001

NB This is the first session and as such was experimental to assess what to record and how to record it. The template on which this record is based was developed subsequently, hence not all fields are complete for the first few records

Location:                                                         Carlton Marshes: Dyke 10

Date:                                                                 02/07/19

Time start:                                                      11.00

Time finish:                                                    12.50

Weather (from BBC weather app):

  • General:                            Fair mild day
  • Humidity:                         –
  • Pressure:                           –
  • Temp:                                18C
  • Temp feels like:                –
  • Wind:                                 Gentle breeze
  • Cloud cover/sun:              Intermittent sunshine and broken cumulus cloud

Observational subject:

Nursery web

Observations:

Web amongst sedge, 18 inches off water in margin. 5m south of 10mph sign. A recently opened egg sac was reported seen on 29/06/19 -three days before this observation. No adult seen. Egg sac present, only two spiderlings seen crawling about web and on sac. Became more active when sun came out.

Impression is that the web is looking tatty -there were some strong breezes in in the area in the three days before this record.

12.05: Little activity

12.50: No further observations to make. Ended.

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Study 2

Fen Raft Spider behavioural study record 002

 

Location:  Carlton Marshes: Dyke 10, immediately by northernmost red and white verge marker post

Date:                                                  08.07.19

Time start:                                        14.00

Time finish:                                      16.10

Weather (from BBC weather app):

  • General:                Mild day, breezy
  • Humidity:              –
  • Pressure:                –
  • Temp:                     17.5C
  • Temp feels like:     –
  • Wind:                      Moderate breeze
  • Cloud cover/sun:   Intermittent cloud, mostly sunny

Subject:

Nursery web with spiderlings. No adult seen.

Vegetation/macro location:

Web in sedge, about 12 inches above water, in margin.

Observations:

The web in study 01 can no longer be seen. This web is further south along the same dyke.

14.00. Spiderlings in a torus formation, the right-hand half shaded, the left in sunlight. Bursts of activity noted in two forms: one as a cascade spreading over the surface of the huddle of spiderlings, the other as a simultaneous burst of activity all over the surface, with individuals at separate points around the huddle simultaneously starting movement. Does this suggest different stimuli for activity? There was no visible trigger for the activity, which always settled down within a few seconds.

14.45. Longer spells of sunlight on web and increased frequency of bursts of activity noted during this period.

14.50. Several bursts of activity occurring within the space of one minute but lasting only a few seconds. These bursts were in the simultaneous pattern.

15.00. It is possible to see now from a different viewpoint that the torus is in fact two separate balls of spiderlings. Learning point: get several viewpoints where possible.

15.30. There are in fact three balls of spiderlings, with one to the left of the others, shaded and well hidden under a broad sedge leaf. The other two are now both unshaded and bursts of activity are noted in both, when the sun emerges. The balls are beginning to join up.

15.55. Sunlight now continuous as clouds have broken up. The two right hand balls have coalesced to form a crescent concave upwards, approximately facing the direction of the sunlight. More a radio telescope shape than a lens shape.

Observed formation shape change consistent with basking behaviour to increase body temperature. This would increase metabolic rate and consequently growth rate.

Increased activity during periods of sunlight consistent with increased metabolic rate and muscular activity with increased body temperature.

Stimuli for activity bursts not known.

16.10 End.

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The hidden third noted ball of spiderlings on the left, shaded by a sedge leaf. The next two are visible and partly obscured.

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Same view closer in and a little later.

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Crescent formation

Study 3

Fen Raft Spider behavioural study record 003

 

Location:                                           Carlton Marshes: Dyke 10. Same as in Study 002.

Date:                                                   09.07.19

Time start:                                        11.30

Time finish:                                      12.15

Weather (from BBC weather app):

  • General:                   Cool slight breeze
  • Humidity:                74%
  • Pressure:                 1022 KPa
  • Temp:                       15C
  • Temp feels like:       –
  • Wind:                        S, 7mph
  • Cloud cover/sun:    Cloudy

Observational subject:

Same web as in 002.

Vegetation/macro location:

As before

Observations:

11.30. Web looks thinner and scantier since seen 18 hours previously. Volume taken by spiderlings seems less, suggesting either less spiderlings or that they are huddling more tightly. Two formations seen, a vertical sausage shape and a separate small ball. Both have a reduced surface area to volume ratio compared with the more diffuse shape of yesterday. No adult seen, very little activity indeed compared with yesterday.

Formation consistent with heat conservation.

12.15: No further activity noted and as I was getting cold (being unable to rapidly reduce my surface area to volume ratio), study ended.

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Study 4

Fen Raft Spider behavioural study record 004

 

Location:                                           Carlton Marshes: Dyke 5b, 8m South of bridge

Date:                                                   16.07.19

Time start:                                        14.00

Time finish:                                      15.45

Weather (from BBC weather app):

  • General:                  Sunny intervals and light winds. Feeling very warm.
  • Humidity:               58%
  • Pressure:                 1018 mb
  • Temp:                       21C
  • Temp feels like:      25C
  • Wind:                       N, 6mph
  • Cloud cover/sun:    V sunny with occasional cloud cover

Observational subject:

2 Balls of spiderlings in a nursery web with egg sac, adult beneath

 

Vegetation/macro location:

Web and spiderlings about 30cm above water surface in water soldier about 1m from east bank. Adult sitting on frogbit on water surface immediately beneath web.

Observations:

14.00. Dark unbanded adult female present

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Initially 2 balls of spiderlings seen in web. Little activity at this time.

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14.20. Adult has moved away from me to next frogbit pad. Can only see back of abdomen and spinnarets. Contrasting light and obscuring leaf cover prevent photo.

14.40 has turned around and is facing me

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15.00. Spiderlings have coalesced into a lens shape roughly facing the direction of the sunlight

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15.40. Spiderlings noted to be very active in full sun

 

Lens formation and increased activity consistent with increased exposure to warmth from sunlight. Suggests active basking behaviour in spiderlings. No active movement of adult into sunlight does not support active basking behaviour in this individual during this study.

14.45 End.

Courtship and Defence

Here is a selection of fascinating photos taken while on a routine nursery web survey. Whilst not a formal behavioural study in the sense of the others written up here, it is worth including here as the most appropriate section overall.

I can’t take credit for the interpretation of the pics and videos -I sent them to Dr Helen Smith who kindly interpreted them for me. These are mostly her words:

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Though this individual is not behaving in any particular way, we were interested to know more about the brightness of its bands which we found striking. He appears to have lost his second left leg. There is also a recorded conversation about its age in a courtship video below -Helen comments on this too.

“Band colour and brightness varies between individuals and is not particularly age-related. The exceptions to this are (1) that tiny juveniles tend to have lighter ground colours and (2) adult females tend to have more subdued band colours, although you do see some brightly banded ones. I’d be interested in trying to quantify the latter!”

“Re the overheard conversation backing this video, this year’s juveniles will only be a max of 3 weeks old and a very few mm long – you’re unlikely even to notice them and they’ll mainly be in the marginal vegetation rather than on the water. Anything vaguely ‘middle sized at the moment will be from last year’s broods.”

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“This couple are indeed a courting pair – the female is already quite gravid. The bobbing in the video is part and parcel of the courtship communication – both sexes do it. In the male it only signals intention but in the female, done (I guess) at a particular frequency or intensity. it can also signal lack of interest! Subtle stuff.”

Here is a nursery web (top right) and below and to the left is a spider. Try and spot it. If you can’t the answer is at the end of this post.

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Here he is -and it’s a male. He has a slim abdomen and clubbed palps like boxing gloves -these contain sperm, ready to inseminate the female, facing him. You can see her legs between the two sedge leaves forming a triangle.

About the above videos (of the same pair of spiders as in the stills), Helen says: “This shows another courtship sequence with the male doing the classic leg-tapping to create concentric waves that signal intention to the female. This can be a very protracted business and the fact that she moved away doesn’t necessarily mean that she’s not interested and won’t accept him in the end.” Apologies for the extra noise -no one was aware I was recording!

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This shot shows a female guarding her nursery. Her body is quite thin because she’s hardly eaten for weeks while carrying her egg sac but her palps are straight and not clubbed as a male’s would be.

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Here the same female is being defensive and guarding her nursery. You can see one of her palps very clearly – and it’s straight, not clubbed at the end. Apologies for the focus -not a lot of control with the apparatus -my camera battery had run out and I used a camera phone held only about 18 inches away, so she had detected my presence. She is holding her right first two legs in a V-sign -very appropriate!

Answer to the spotting question: He’s at the bottom of the photo, to the right of the triangle formed by the two most right hand sedge leaves. In the apex of that triangle you can partly see a female facing him.