Do animals bite more during a full moon? Retrospective observational analysis
BMJ 2000; 321 doi: https://doi.org/10.1136/bmj.321.7276.1559 (Published 23 December 2000) Cite this as: BMJ 2000;321:1559All rapid responses
Rapid responses are electronic comments to the editor. They enable our users to debate issues raised in articles published on bmj.com. A rapid response is first posted online. If you need the URL (web address) of an individual response, simply click on the response headline and copy the URL from the browser window. A proportion of responses will, after editing, be published online and in the print journal as letters, which are indexed in PubMed. Rapid responses are not indexed in PubMed and they are not journal articles. The BMJ reserves the right to remove responses which are being wilfully misrepresented as published articles or when it is brought to our attention that a response spreads misinformation.
From March 2022, the word limit for rapid responses will be 600 words not including references and author details. We will no longer post responses that exceed this limit.
The word limit for letters selected from posted responses remains 300 words.
In the Discussion you say "In our study we showed that an association
exists between the lunar cycles and changes in animal behaviour and that
animals' propensity to bite humans accelerates sharply at the time of a
full moon", but I see nothing in the article to support this statement.
You have measured the frequency of bites, but not the circumstances.
You could equally draw the (unsupported) conclusion that "the propensity
of humans to provoke animals to biting accelerates sharply at the time of
a full moon".
You have shown a probable relationship between animal bites and the
lunar cycle, in one environment, without circumstances. Therefore, the
conclusion that "the propensity to bite" is increased is unsupported in
the article, which does not measure "propensity", only frequency.
Competing interests: No competing interests
Editor,
In response to two articles with contradictory results that were
published in the BMJ (1,2) on the effect of lunar phases on the frequency
of animal bites, and the discussion that followed them, we undertook an
analysis in order to test the same hypothesis with data derived from a
large
Emergency Department Injury Surveillance System (EDISS) in Greece. The
first of the above articles stratified the number of bites in 10 periods
of moon and found a significantly increased risk of bite at or near full
moon. No adjustment for weekday or other variables was made. The second
article stratified number of bite cases by weekday, and full versus no
full moon, and found no significant
increase in risk. In comparing the two methods, therefore, the one
addressed possible weekday effect but not the continuum among lunar
phases, whereas the other addressed the continuum of lunar phases, but not
the weekday effect.
We believe that both, weekday effects and the continuum of lunar
phases, should be addressed simultaneously in such a problem, and that
ignoring either issue, as done in both articles, can possibly create
extraneous relations between
number of bites and full moon simply because of differential exposure. For
example, adjusting for weekday is necessary because more people tend to be
outdoors (which could imply higher exposure to bites) systematically on
certain days (e.g., weekends) and not on others. Similarly, in certain
cultures, more people tend to be outdoors at full moon, though not
necessarily at periods near full moon, and the adverse impact of such
differential exposure would be less
when looking at the seasonality of lunar phases, rather than simply at
full versus no full moon.
To address these two issues simultaneously, we have conducted a more
appropriate analysis, and with a new from injury cases inflicted by dog
bites, and registered in EDISS, Greece. A total of 2642 such cases had
occurred within the window of earliest to latest full moon between
1/1/1996 and 12/31/1999. For each case, we obtained the gap time between
the day of bite injury and the day of the
immediately preceding full moon. We classified these gap times, which
ranged from 0 to 29 days, to 10 periods, in analogy to the first article,
with the minor exception that each of our periods covered three days: a
bite occurring at
gap of 0 days (full moon), 1, or 29 days was labeled period 5; gaps of 26-
28 days were assigned period 4; and so on for the other periods. Finally,
we cross-classified the cases into the two-way table of moon period (1-
10), by the
weekday at which the bite occurred. We analyzed the data with a Poisson
regression allowing for possible simultaneous (i) effect of weekday, and
(ii) effect of seasonality of the 10 moon periods on bite number, whereby
we estimated the time (which period) of peak and the intensity of the peak
of
seasonality (procedures and data are available upon request).
The results showed evidence for seasonality, with a relative risk of
1.13 for highest versus lowest risk of bite (P=0.028; 95% CI: [1.01,
1.26]). However, the timing of this highest incidence adjusting for
weekday effect, was estimated at period 1 (17-19 days), with 95% CI:
periods [10,1,2], i.e., [14-22] days after full moon, thus excluding
periods at or near full moon.
Although additional unknown factors may underly the discerned
seasonality pattern during days 14-22, this is always possible in
observational studies, and informed judgment is based on the existing
evidence after known concerns are suitably addressed. The evidence based
on our results is that there is no increases risk of bites at or near full
moon.
References:
1. Bhattacharjee C, Bradley P, Smith M, Scally AJ, Wilson BJ. Do
animals bite more during a full moon?
Retrospective observational analysis. Br Med J 2000; 321:1559-61.
2. Chapman S, Morrell S. Barking mad? Another lunar hypothesis bites
the dust. Br Med J 2000; 321: 1561-3.
Competing interests: No competing interests
Sir,
Bhattacharjee et al’s paper on the relationship between dog bites and
lunar phase makes interesting reading and demonstrates a strong
relationship between the two in Bradford1. We decided to test whether this
hypothesis would be substantiated by an analysis of data from the All
Wales Injuries Surveillance System (AWISS)2.
We analysed both dog and human bite victims attending emergency
departments in Wales between January 1999 and June 2000 and followed
Bhattacharjee’s methodology.
There were 2887 dog bites and 550 human bites. There was considerable day to day variability in
the number of bites. The slight peak at day 0 (full moon) and day 1 (17% excess) is not
statistically significant, a finding that is in clear contrast to that in
Bradford.
Bhattacharjee et al may have furthered Noel Coward’s observation that
‘Mad dogs and Englishmen go out in the midday sun’, by adding ‘and bite at
the full moon’. Fortunately, this type of behaviour appears to be
restricted to the eastern side of Offa’s Dyke.
Rhys Pockett, Research Assistant
Sarah Jones, Lecturer
Ronan A. Lyons, Senior Lecturer
Department of Epidemiology, Statistics and Public Health, University of
Wales College of Medicine
Peter Richmond, Consultant in Emergency medicine
University Hospital of Wales, Cardiff.
1. Bhattacharjee, C., Bradley, P., Smith, M., Scally, A. J., Wilson,
B. J. Do animals bite more during a full moon? Retrospective observational
analysis. BMJ 2000; 321:1559-1561 (23 December)
2. Lyons R. All Wales Injury Surveillance System (AWISS). Eurorisc
newsletter (European
review of injury surveillance and control) 1998;3:6.
Competing interests: No competing interests
Editor - I read with interest the two articles on frequency of dog
bites related to seasonal changes, in particular the lunar cycle (1,2).
However, despite the humerous nature of this particular edition of the
Journal, I do feel that the authors of one of the papers (2) may have
thrown out the baby with the bathwater. They demonstrate that there is no
association between frequency of dogbites and phase of the moon, nor day
of the week, in Australia.
Nevertheless, there is something cyclical about the frequency of reported
dogbites, although admittedly it is not in phase with lunar changes. Even
if you draw a cutoff line below 10 bites per day, there are clearly 12
sharp peaks of bite frequency as high as 15 to 20 per day, lasting only a
day or so, occuring on a regular basis throughout the year. Do they occur
on the first day of the month, rather than the lunar cycle, as there are
12 months but 13 lunar phases in one year?
If I was told that the graph was actually a strip of poor quality ECG
recording, I would say that the patient has clear QRS complexes, is
regular enough to possibly be in sinus rhythm , but there is a lot of EMG
muscle artifact noise.
I feel that the data should be subjected to more detailed signal analysis
and other mathematical techniques which have been developed to recover
information from noise to tease out further the demonstrated regular
pattern of dogbite frequency. It my reveal some fascinating insight into
the habits of dogs and/or humans in Australia.
AS Laurence, Consultant Anaesthetist, Preston, UK.
References:
1. Bhattacharjee C, Bradley P, Smith M, Scally AJ, Wilson BJ. Do
animals bite more during a full moon? Retrospective observational
analysis. Br Med J 2000; 321:1559-61.
2. Chapman S, Morrell S. Barking mad? Another lunar hypothesis bites
the dust. Br Med J 2000; 321: 1561-3.
Competing interests: No competing interests
Battacharjee et al. think they have shown an association between the
lunar cycles and animal behaviour such that animals bite humans more round
about the time of a full moon.
The leap from their findings to their conclusions is a great one and many
factors have not been considered, measured or excluded.
What they did show was that more people attended the A and E Department
with bites (excluding human and insect) at the time of full moon. Which
animal bit these people is not stated.
How many bites occurred at home? What would it all mean if there were more
animal bites at home at the time of a new moon and hardly any at the full
moon?
Were the owners bitten or were the patients strangers?
Which animals were biting.? Chapman and Morrell (2000) showed the highest
peak for dog bite admissions in Australia to be over the New Year and no
positive relationship between the full moon and such bites.
On New Years eve we had a small party and I, after I had partaken of a few
glasses of vintage champagne, gave our dog, a ball, which flashes and
plays various alarm/siren sounds each time it bounces. It was not a full
moon and despite having a “mad half hour” he bit no one.
Chapman, S and Morrell, S. Barking mad? Another lunatic hypothesis
bites the dust Brit. Med. J. 321 (7226): 1561 2000.
Dr Richard Sloan M.B., B.S., B.Sc., Ph.D., M.R.C.G.P.
Associate Director of Postgraduate General Practice Education (Yorkshire),
Principal, General Practice
Competing interests: No competing interests
The moon has influence on the 4 levels of life: mineral, vegetal,
animal and human.
On the mineral, we see the influence on the sea with the ups and downs
towards the position of the moon.
On the vegetal, it is know that, as the sun does, also the moon has
influence on growing.
For explaining the influence over the animal world, it has to be explained
that astrologically we have two types of energy : the energy of the sun
that is energy of giving, and the energy of the moon that has nothing to
give but that it receives from the giver. It is compared to the human
being in his two inclination : the egoism, and the altruism.
The first is an animal tendency , and the second a purely uman one. So
that the tendency of receiving is an animal one and is representated by
the moon astrologically. The conclusion is that when the moon is
increasing its influence over the earth, the animal tendencies are growing
as is the caracteristic that moon represents, so the animal life has more
vivification in these days.
Also humans are influenced by the moon , as we see in the women's
fertility.
Jews have their calendar based on the moon. The Kabbalah explains that
there i a strong spiritual influence from the moon on human spiritual and
emotional behaviour, and the greeks when they conquered Judea 2500 years
ago they prohibited the jews to maintain the jewish calendar because they
were afraid that otherwise they won't subjugate them , as it happened.
Sincerely
Yehiel Linn
Competing interests: No competing interests
This report does not support the conclusion that "an association
exists between the lunar cycles and changes in animal behaviour and that
animals' propensity to bite humans accelerates sharply at the time of a
full moon." The only thing demonstrated is that more people experience
animal bites at the time of full moons. There are no data presented
regarding changes in animal behaviors that would place them in proximity
to humans and facilitate an altercation. Personally I enjoy going for
nighttime runs when the moon is waxing; in so doing I see raccoons,
skunks, and rats that I rarely see otherwise. Indeed, I offer the
following counter hypothesis: An association exists between the lunar
cycles and changes in human behavior, and this increases the opportunity
for humans to encounter animals that they would otherwise not have been
exposed to.
Competing interests: No competing interests
Re: The conclusion is unfounded
I must agree the conclusion is unfounded. I agree the
analysis demonstrated an association but in no way
did it address or prove causation. Many odd behaviors,
human and animal, have been assigned to the lunar
cycle. It is not a suprise to see a well documented
study of one particular event which shows a sharp
increase. I am sure there are others. It would be
interesting to compare the "victims" of animal bites
during the full moon. It may be the humans are the
ones who have a behavioral change.
Competing interests: No competing interests