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Introduction
The Basenji is the only breed, out of 150 currently recognized by the AKC,
to have an annual estrus cycle. Unlike the other breeds that have two
estruses anytime during the year, the Basenji’s annual estrus is seasonal.
For the most part, estrus occurs within the months of September and
October for Basenjis living in the Northern Hemisphere. Breeders have also
noticed a second estrus sometimes occurs around March or April. In England
many Basenjis have a second estrus (Burns, 1952). This has created some
concern that the Basenji is losing its annual cycle since leaving Africa.
The tendency for a second annual cycle has existed in Africa and in the
Bitches imported from Africa.
The estrus cycle in Africa
Using birth dates of Basenjis imported from Africa (Coe, 2001), two
figures were created showing the estrus of the Imports' Dams in Africa.
Figure 1A shows the occurrence of estrus for Basenjis north of the
equator, and figure 1B for those south of the equator. The estrus cycle
for Basenjis south of the equator is opposite of those north of the
equator. As noted by Ford (1997) an American Basenji imported into
Rhodesia switched it’s annual estrus to the spring. The reason why this
occurs will be described in a future article. To find the estrus start
date for the Imports' Dams two methods were used. If only the month and
date of the Imports birth was known, then the date of estrus was
determined by counting back two months. For those Imports with a complete
birth date, date of estrus was determined by counting back 70 days using
the same method employed by Scott and Fuller (1965). Only those Imports
where the area discovered in Africa was known were included. Two African
Imports were also included who had litters in Africa, one north and the
other south of the equator. The date for the start of estrus for these two
African Imports was calculated from their litters birth date.
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Number of bitches
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FIGURE 1A.
Occurrence of estrus for African Imports' Dams and one Import having
litters north of the equator in the DR Congo, S. Sudan, Nigeria, Benin
or Liberia from 1937 to 1996. |
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6 |
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5 |
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4 |
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3 |
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2 |
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1 |
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Month estrus occurred => |
JAN |
FEB |
MAR |
APR |
MAY |
JUN |
JUL |
AUG |
SEP |
OCT |
NOV |
DEC |
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Number of bitches |
FIGURE 1B. Occurrence of estrus for African
Imports' Dams and one Import having litters south of the equator in
the DR Congo from 1935 to 1937. |
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2 |
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1 |
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Month estrus occurred => |
JAN |
FEB |
MAR |
APR |
MAY |
JUN |
JUL |
AUG |
SEP |
OCT |
NOV |
DEC |
African rainy season indicated by months in bold (Dry
season can vary from 4 to 2 months depending on latitude).
The number of estrus recorded (30) is probably not high enough to be
statistically significant, but a trend does appear. In figure 1A the
majority of estruses occur around November resulting in most litters being
born during the dry season. What is most interesting is that a second
estrus peak shows up in March through May. Most of these litters would be
born in the middle of the rainy season. For the bitches south of the
equator, figure 1B shows estruses occurs from January to May. Their
litters were born during the end of the rainy season and start of the dry
season.
Imported African Bitches
To see if the pattern in Africa would continue with the Imported African
Bitches having litters out of Africa the same methods in compiling figures
1A and 1B were used to create figure 2. All litters were born north of the
equator. There were 19 bitches having a total of 41 litters.
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Number of occurrences |
FIGURE 2. Occurrence of estrus for Imported
African Bitches having litters in the U.K., U.S., Germany, or Italy
from 1937 to 1999. |
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17 |
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16 |
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15 |
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14 |
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13 |
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12 |
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11 |
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10 |
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9 |
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8 |
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7 |
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6 |
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5 |
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Month estrus occurred => |
JAN |
FEB |
MAR |
APR |
MAY |
JUN |
JUL |
AUG |
SEP |
OCT |
NOV |
DEC |
The bitches imported out of Africa show a similar
pattern as figure 1A. Two peaks appear during the same time of the year.
The majority occurred between August and November with a smaller number
between March and May. One of the original imports was recorded having a
litter about 5 months apart. Amatangazig of the Congo had borne a litter
on January 1, 1942 and on June 10, 1942.
Conclusion
While the Basenji for the most part has a seasonal annual cycle there is
a tendency for some Basenjis to have a second estrus. This pattern
originated in Africa and continued in the first generation out of Africa.
Bibliography
Burns, M. 1952. The Genetics of the Dog. Farnham Royal, England:
Commonwealth Agricultural
Bureaux. viii + 122 pp.
Coe, S. (ed.). 2001. The African Stock Project. Newtown, PA:
Basenji Club of America. [various
paginations]
Dean, R. 2002. [Basenjis_African]West Africans – history. Email to
Basenjis_Africans Yahoo
group March 13, 2002.
Ford, E. 1997. The Complete Basenji. N.Y.: Macmillan Pub. Co. 160
pp.
Scott, J. P. & J. L. Fuller. 1965. Genetics and the Social Behavior of
the Dog. Chicago:
University of Chicago Press. xviii + 468 pp.
Scott, J. P., J. L. Fuller & J. A. King. 1959. Inheritance of annual
breeding cycyes [sic: cycles] in
hybrid Basenji-Cocker Spaniel Dogs. The Journal of Heredity,
50:255-261.
Revised from
The Basenji
Volume XXVIII Number 10 October 2002 p. 10
Copyright © 2002 Bar Harbor Media, All Rights Reserved
Used with permission. |