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A Presentation
on Strategies
for Long-term
Reproductive
Success with
Boa constrictor
ssp. |
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Theory
There are two
main (competing?)
theories in
the breeding
of Boa c.
ssp.. First
is the concept
that if the
female is large
enough and has
sufficient body-reserves
she will ovulate,
become receptive
to breeding,
breed and have
young (or perhaps
the breeding
precedes and
precipitates
ovulation).
This practice
relies almost
solely upon
the progression
of the so-called
'fat-ovulation-cycle'
to induce reproduction.
Keepers employing
this usually
place little
emphasis upon
providing seasonality.
Often, people
use this routine
simply by default.
Temperatures
are kept high
and feedings
frequent and
regular in order
to grow their
boas as rapidly
as possible
to attain 'breeding
size’ (a
near meaningless
term, see Note
1 below).
Many reptiles
have responded
to this practice
(in terms of
initial reproductive
success) in
captive colonies.
In the boas
some success
has also been
achieved with
this method.
Second is the
use of seasonality
in inducing
successful reproduction.
The animals
are given shorter
days, cooler
temperatures
and less food
during one part
of the year
(usually Winter)
and higher mean
temps, longer
daylight hours
and more frequent
feedings during
the balance
of the year
(see Notes
2
and
3).
The idea is
that the onset
and progression
of the changing
temperatures
and other routine
precipitates
hormonal and
or behavioral
changes in mature
healthy boas
resulting in
breeding, ovulation
and birth. Advanced
keepers of boas
often report
enhanced breeding
rates when incorporating
seasonality
(sometimes simply
called cooling)
into their husbandry
practices.
We strongly
believe in providing
seasonality
for boas being
maintained for
long-term breeding
success. The
reasons for
this are:
1) in our observation
size is related
to maturity
in the Boas
but is secondary
to age. So maintaining
a high metabolic
rate in growing
boas year-round
in order to
increase mass
in young boas
is not needed.
2) In nature
(as demonstrated
by import patterns
and other observations)
boas do have
young mainly
within certain
times of the
year, corresponding
to seasonal
patterns.
3) Locality
populations
of boas drawn
from widely
different places
in their natural
range clearly
respond (in
terms of behaviour
patterns) to
varying degrees
to (the application
of) seasonality
at our latitudes.
4) We have enjoyed
a consistently
higher rate
of breeding
success (and
predictability)
with the boas
using seasonality,
including with
those sub-species
and localities
considered more
challenging
in culture.
(See
Note 4)
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Theory in practice |
The
Boas as a group
have produced
viable young
in captivity
under a broad
range of conditions.
Feeding, age,
size, captive
environment
and seasonality
all play important
roles in the
process. I also
hinted that
some disagreement,
even competition,
may exist among
those keepers
and breeders
practicing either
the ‘feed
to breed’
regimen or the
use of seasonality
in inducing
successful reproduction
in their colonies.
To a large extent
one’s belief
in which practice
will render
best results
hinges upon
which group
of Boas is the
focus of your
efforts and
experiences.
In very broad
terms the imperator
subspecies requires
much less seasonality
to produce young.
At northern
latitudes and
in many facilities
a pattern of
seasonal change
sufficient to
aid in reproduction
in most imperator
may be experienced
even without
planning or
action. However,
the constrictor
group responds
best to a much
sharper gradient
in temperature
and (to a somewhat
lesser extent)
photoperiod.
Other subspecies
in captive culture
more closely
follow the pattern
of one or the
other of those
main groups.
Closer observation
of these animals
yields a better
theory. It is
not the subspecies
but rather the
natural environment
of origin that
determines whether
or not controlled
seasonality
is more needed
to achieve repeated
breeding success.
As an example
B. c. imperator
from the upper
Yucatan Peninsula
will breed consistently
in the mainland
U.S. with little
attention to
seasonality.
Imperator from
higher altitudes
in N. Chihuahua
or Sonora, Mexico
can require
a near 25% reduction
in mean temperatures
from those experienced
at the height
of Summer. And
while inbreeding
and intergrading
Boas in captivity
has blurred
the lines between
some populations
you will discover
that all the
boas will respond
favourably to
seasonality
and in some
populations
it (seasonality)
is a near necessity
for successful,
reproducible
breeding.
It is plain
to us that both
the ‘fat-ovulation-cycle’
and the onset
of seasonal
change have
effect upon
and play important
roles in breeding,
ovulation and
birth in the
Boas. With this
in mind our
breeding regimen
involves the
carefully integrated
application
of both of these
practices and
preparing boas
for long-term
breeding in
captivity is
begun at an
early age.
Boas raised
here are fed
conservatively
and subjected
to a simple
form of seasonal
change. Mean
temperatures
and photoperiod
(daylight hours)
are lowered
about 15 percent
for the months
of December
and January.
Feeding is scheduled
in this fashion;
boas are fed
when hungry
and not fed
again until
all signs of
the previous
meal have subsided
and the animal
again appears
hungry. If there
is any doubt
as to whether
or not a boa
is again ready
to feed, we
wait another
day or two.
We strictly
avoid any sign
of obesity in
growing boas
and reduce feedings
to individuals
which appear
overweight.
Prey-size selection
is as follows,
a meal is too
small if it
does not show
as a noticeable
lump or swelling
just after ingestion.
A prey item
is too large
if the animal
is unable to
crawl or coil
normally after
eating or during
digestion. If
you consider
this information
carefully you
will see that
it is self-adjusting
for almost any
season or condition
your boa is
in. In first-year
babies our feedings
average about
every ten days.
(See Note
5 below).
As the boas
grow they consume
larger meals
and feedings
are less frequent.
By adulthood
females are
fed a substantial
meal perhaps
twice each month
for only about
ten months of
the year, less
when gravid
(see Note
6).
Mature breeder
males feed as
little as ten
or twelve times
in a calendar
year. Boas raised
according to
our simple rules
will mature
in three and
one-half to
five and one-half
years with most
of the imperator
groups maturing
earlier and
the constrictor
localities somewhat
later.
Maturing boas
are not placed
on special or
extra-feeding
schedules. It
is our observation
that really
heavy boas are
not needed for
breeding and
obesity is statistically
linked to sub-optimum
breeding results.
In males of
any subspecies
extra size and
weight is strongly
contraindicated.
Of course breeding
requires peak
condition so
be sure your
boas are fed
to proper weight.
Experience shows
us that this
cannot be best
achieved by
feeding heavily
during the Spring
or Summer months.
Boas may rapidly
gain weight
if fed aggressively
during this
period but the
growth may not
be directed
towards maturity.
In addition
for those individual
boas that do
respond strongly
to the ‘fat-ovulation-cycle’
you may miss
the breeding
opportunity
if they reach
peak weight
off-season.
Also, the males
may not be in
condition to
breed. A much
higher percentage
of ‘slugs’
or infertiles
as well as other
birth problems
does occur in
these off-season
breedings. The
goal is to have
the potential
breeders reach
optimum weight
just as the
seasonal changes
begin to have
effect upon
breeding behaviour.
A long-term
program of feeding
is used. As
a simple example,
visualize your
4-6 year-old
boas as perhaps
requiring 25
rats (much less
for the males)
to grow properly
and attain breeding
weight. Instead
of feeding them
heavily during
the warm months
spread out the
feeding in the
24 weeks between
June and December.
Some individuals
(particularly
recovering mothers)
will display
a very aggressive
feeding pattern
in the hot months;
aside from giving
an extra portion
or two to very
thin individuals
we do not give
more food to
these boas,
we trust in
the program
to bring the
animals to proper
weight in time
for the seasonal
activity.
You will have
to observe your
climate and
set-up and adjust
this to your
conditions but
in our collection
mature potential
breeder boas
begin a cool-down
and decrease
in photoperiod
on or about
the first week
of November.
In our experience
the constrictor
sub-species
responds best
after a full
20% reduction,
we try to achieve
this goal by
the week of
Christmas. Imperator
boas will normally
begin to respond
after as little
as a 12% change.
If your normal
highs are 94deg
(f) then by
the first of
January a high
in the mid to
upper 70s will
be appropriate.
Lows should
be allowed to
reach 70 or
even 65 degrees,
especially in
the constrictor
subspecies.
As much as possible
you should check
for these target
temperatures
in the animal.
Relative mass
is a factor
in temperature
drop and rise.
It may take
longer for your
boas to reach
mean low temperatures
than you think.
Be advised that
body temperatures
below 60 degrees
(f) and above
approximately
95 degrees (f)
are potentially
harmful to your
boas.
Here are
some specific
observations
on breedings:
Imperator males
will begin courting
most mature
females in condition
to breed just
before or just
after minimum
temperatures
are achieved.
They breed strongly
on temperature
rise, with 75
degrees often
being a trigger
to attempt copulation.
Copulation and
serious courtship
will frequently
cease at temperatures
above 85 degrees.
Constrictor
pairs wait another
few weeks and
will many times
copulate at
mean low temperatures.
Conditions above
78 or 80 degrees
will end intromission
in most of our
groups. Again,
we are discussing
body temperatures
and few absolutes
regarding the
effects of specific
temperatures
on breeding
behaviour are
known. But the
data given here
could be extremely
useful in designing
a serious breeding
program.
At our latitude
and in our collection
breeding trials
begin in December
and most all
breeding is
concluded by
the middle of
March. Most
successful breeding
occurs between
Christmas and
Valentine’s
Day. After copulation
is observed
we begin to
elevate the
female’s
temperatures.
As this condition
progresses the
male loses interest
in breeding
and is removed.
Individuals
of some groups
will demonstrate
a marked trend
to breed outside
of this period.
These variances
most often occur
closer to the
time temperatures
begin to return
to normal highs.
This has been
observed in
our Trinidad
and Suriname
constrictor.
We watch for
this and adjust
the timing of
their feeding
schedule and
breeding trials.
For some anxious
keepers a three-month
window of breeding
opportunity
is too much
of a constraint
and they will
attempt breeding
their stock
throughout the
year. Sometimes,
especially if
the animals
have not been
exposed to seasonality
during their
life, these
breedings will
produce young.
So, why not
attempt off-season
breeding? My
answer is that
our methods
represent a
pro-active approach
to reproduction
in Boa. The
predictability,
higher success-rate
and reduced
complications
achieved by
using seasonality
and planned
feeding and
growth to induce
reproduction
outweigh the
occasional chance
of bringing
a litter to
market a month
or so early.
Lastly, we place
very little
confidence in
the idea of
counting the
days from intromission
or post-ovulation
shed-cycle to
determine parturition
or birth-date.
This could be
due to the highly
varied genetics
in our breeding
groups as compared
to (as an example)
those found
in a colony
producing amelanistic
imperator. Also
we know we allow
our incubating
females a much
larger temperature
gradient than
many keepers
will. Suffice
it to say that
we have seen
viable births
without complication
as soon as 97
days and as
long as 252
days after breeding.
And expectant
mothers in our
care may shed
once, twice,
three times
or even in rare
instances not
at all before
giving birth.
I would sincerely
appreciate more
real insight
into this phenomenon.
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NOTES |
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1: Accepted breeding
size varies
among the localities
of Boa sp. The
smallest Boa
may deliver
young without
complication
at barely over
three feet in
length and less
than 2KG in
mass. Others
will be substantially
larger. It is
our observation
that size is
not nearly as
important a
factor as age
in Boa maturity.
As early as
1979 Neil Ford
of UT Tyler
produced data
showing that
live-bearing
snakes encounter
the same difficulties
giving birth
at a premature
age as do many
other animals.
Sub-mature snakes
of apparent
sufficient size
to carry young
produced fewer
viable young
and consumed
more body reserves
than older mothers
of similar size.
And experience
is also a positive
factor; more
young of comparatively
larger mass
are born to
older experienced
mothers. Inducing
ovulation in
young boas under
about age 3
years by feeding
heavily is risky
and over the
course of the
project may
not yield more
viable babies
than waiting
for full maturity. (Back)
2:
Misting, spraying
or raining on
Boa c. ssp.
paired for breeding
may or may not
have any effect
on captive reproduction.
Certainly the
onset of the
wet season has
an impact on
these animals
in nature. Possibly
it (misting)
would produce
more identifiable
results in stimulating
breeding in
captivity if
it was supplied
over the life
of the animals
as part of their
seasonally adjusted
climate pattern.
We do not employ
this here. Theories
about boas giving
birth during
rainstorms as
a way of concealing
the young do
not stand up
to the scrutiny
of people more
familiar with
the natural
history of Boa.
(Back)
3: Barometric
(atmospheric)
pressure changes
are reported
to have an effect
upon boa breeding
behaviour and
even parturition
(birth). We
also have observed
this but it
does not appear
to be statistically
significant.
Parturition
date has much
more to do with
breeding and
inception date
and conditions
during incubation
than current
(local) conditions.
(Back)
4: One
important note;
reproductive
success with
Boa c. ssp.
is impossible
without healthy
animals that
feel secure
in their surroundings
regardless of
what steps are
taken to induce
breeding. Any
successful breeding
program will
be based upon
proper caging,
cleanliness,
freedom from
undue stress
and disease
and top-quality
food. This is
in itself no
mean task and
cannot be left
to chance. Hats
off to those
who are able
to provide this
environment
to their Boas.
For the balance
of the hobbyists
who may have
difficulty maintaining
a quality life
for their boas
or other captives…..
get to work! (Back)
5: The
very first feeding
of neonate boas
should not be
attempted until
a week after
the post-birth
shed cycle is
completed. Feeding
baby boas too
early can induce
a cycle of regurgitation
and poor weight
gain that may
never be overcome.
It is also observed
that newborn
boas can be
fearful of meals
offered and
it may subsequently
take considerable
effort to convince
these babies
to feed. (Back)
6: Caution,
it has been
observed that
feeding pregnant
boas too large
a meal or too
near parturition
can cause pre-mature
birth. (Back)
— A. Rentfro |
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