Effects of the moon on animals
Casual observations and unsubstantiated folklore
The scientific evidence
This page is still in its early stages. References which I have
quoted in full on this page are ones I haven't managed to look up yet.
Some of this stuff is relevant to the page about
Casual observations and unsubstantiated folklore
The Miskito Indians of Eastern Nicaragua, believe that all animals
respond to the tide, that the woodpecker pecks when the tide is changing,
and that hunting and fishing is best at the rising tide but not at
new moon. They also believe that
crops should be planted and harvested at certain phases of the moon.
In a similar way, South sea islanders believe that whale sharks are most
caught a few days after full
Another belief is that castrating and weaning of
animals should be done at certain phases of the moon, or when
the moon is
in a certain sign of the zodiac. See the links below for more on this.
The scientific evidence
Numerous scientific papers have been written on tidal rhythms in
marine animals. Crabs and other crustaceans
feature in these studies
quite a lot, probably because they are affected by the tides
In these cases, the animals seem to be following two rhythms: a daily
(24 hour) rhythm, and a tidal (24.8 hour) rhythm*.
These rhythms persisted in the laboratory under conditions of constant
light and temperature.
In many crustaceans, renewal of shells, sexual activity, and regeneration
of lost limbs all follow lunar tidal rhythms (Nouvel, H. (1945)
Bull. Inst. Oceanogr. Monaco, 42 878;
Wheeler, J.F.G.J.Linn.Soc.Zool., 40 325).
Activity of crabs has been measured, usually by placing the crabs in a
tray, balanced on a knife edge, and connected to a rotating drum to
record any movements which the crabs make.
Fiddler crabs often became more active at the times when their burrows
would have been uncovered by the tide.
Activity of the shore crab Carcinus maemas L. follows a lunar
tidal rhythm (Naylor, E., Atkinson, R.J.A. and Williams, B.G.
J.Interdiscipl.Cycle Res. 2 2: 173-180), as does
the crab Sesarma .
Oxygen consumption in the Fiddler crab, Uca pugnax follows
a daily rhythm and a tidal rhythm.
Webb, H.M. (1971) J.Interdiscipl.Cycle Res. 2 191-198).
Tidal rhythms of activity have also been observed in fish, such as
Blennius pholis ; amphipods
(Rao, K.P. (1954) Biological Bulletin 106 357-9);
In these examples, the animals may be responding to moonlight, gravity
effects and possibly changes in temperature. In some cases the rhythm
when they are kept in the laboratory under constant light and temperature,
in other cases this is not so. Tidal rhythms may be modified daily rhythms,
as in some cases the animals switch from a 24.8 hour tidal rhythm, to a
24 hour rhythm in the lab.
A study by Korringa (Vakblad Biol. Sept. 1947 129-137) apparently
showed that oysters could respond to changes in the force of gravity associated with the
tides. I vaguely remember reading about something like
this in Supernature
by Lyall Watson. Oysters were moved miles inland to Iowa or somewhere,
began opening and closing their shells at the time that the tides would
rise and fall, if there were tides in Iowa. I also read a sceptical article suggesting that this was
simply due to a change to the circadian cycle, that often happens when
animals are taken out of their natural environment
Fiddler crabs also change colour daily, becoming lighter at night and darker
in the day. On top of this 24 hour rhythm is a 12.4 hour tidal rhythm,
which relates to the time at which their burrows are uncovered by the tide.
The two rhythms coincide every 14.8 days, producing a noticable
semi-monthly colour change. This could be relevant to the next section:
The phase of the moon seems to influence the behaviour of a number of
animals. In many cases, the animals are simply responding to the changes in
light, which may (for example) make them more visible to each other
or to predators, but it is possible that there are monthly circadian
operation (as in humans), or that the animals are responding to gravitional
effects. As in the case of
The moon's effects on plants, I am a bit sceptical of the latter
The Palolo worm, Eunice viridis is found on several coral islands in
the South Pacific, especially near to Samoa and the Fidji Islands.
The palolos reproduce by swarming during the last quarter of the moon in October and November.
The terminal parts of their bodies drop off and
float over the surface of the water, releasing sperm and eggs.
This event is/was so important to the inhabitants of the Banks Islands, that
it featured in their Lunar Calendar.
A similar species is found in the Atlantic, but here swarming takes place
in June or July during the first quarter of the moon.
I have it on good authority
that spiny lobsters in the red sea avoid foraging at full moon because of the
threat from sharks.
Clunio marinus has reproductive cycles synchronised with the phases
of the moon (Caspars, H. (1951) Arch.Hydrobiol 416-594)
The breeding behaviour of
the Malayan Black Rice Bug seems to be synchronised with the phases of
the moon. More young males rice bugs are caught in light traps at full
moon than at any other time. Black rice bugs are serious pests of rice in
the far-east . I
suppose this may be similar to the behaviour of moths which fly into lights:
They navigate by the light of the full moon, so when they encounter
other bright lights, they fly around them in circles.
Gerbils in the Negev desert forage more for seeds at new moon than at
full, because at full moon they are far more likely to be caught by owls
The moon seems to affect trout fishing. Between 1959
and 1968, the largest catches of trout in lake Neuchatel in Switzerland
were just before or just after new moon, and the smallest catches
were during full moon (Quartier, A.A.(1970) Influence de la lune sur la
peche des truits du lac de Neuchatel. Rapport de la Bibliotheques
et des musees de la ville de neuchatel).
Horse breeders have claimed that mares are more likely to conceive at full moon,
but so far research on this has been inconclusive. I own a female
donkey and you could set the calendar by her.
When there was a male donkey in the area I learned to tie her up very securely on
winter full moons! Strangely, she once went into heat in July during a
solar eclipse. Winter is the usual donkey mating season.
Research in Japan has shown that dairy cows are significantly more likely to be
born at full moon. You can read the article here
Lunar Cycle Influences Spontaneous Delivery in Cows
Tomohiro Yonezawa ,
Published: August 31, 2016
*12.4 hours is the time between two successive high or low tides.
24.8 hours is a "lunar day".
Tides are greatest at new moon, when the gravitational pull of the sun and
moon are both acting in the same direction. Because the moon is moving
relative to the earth and the sun, the "lunar day" is not precisely
Links to other sites on the web
Dreamaker Farms breed Black/White Tobianos and Buckskin Missouri Fox
Trotting Horses. Foals are weaned and castrated according to
the phase and sign of the moon.
The old farmers almanac
Contains information on castrating and weaning animals by the phase of the
Castrating, moon phases and signs
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