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A large number of river otter (Lontra canadensis) males were collected
from areas of high and low contaminant concentrations throughout western
Oregon and Washington during the fall and winter of 1994-99. Few significant
non-reproductive organ morphometric differences were found in the large series
of male otters collected, except for adrenal gland, lung, pancreas, thymus and
thyroid gland mass in adult males. With respect to reproductive organ soft tissue
mass, Oregon males were significantly heavier. Oregon yearling and adult male
otters attain reproductive readiness approximately two weeks earlier than their
Washington counterparts, explaining these size differences. Juvenile males from
Oregon also appeared to be more developed than Washington juvenile males.
Male river otter hepatic contaminant concentrations exhibited significant
regional differences, with males from heavily populated and industrialized regions
of western Oregon and western Washington having higher concentrations of
polychlorinated aromatic hydrocarbons. Also, otters collected from areas of
intensive agriculture had significantly higher organochlorine insecticide and
metabolite (OCs) concentrations. Mean liver concentrations of mercury were
similar among regions for both juvenile and adult male otters, except the Lower
Columbia River males which were significantly lower for both age classes.
Although some mean mercury concentrations were elevated (3.6-
13.8 μg g-1, dw), they were well below concentrations considered toxic.
Juvenile male river otters were prepubertal during their first year of life, as
signified by the absence of testicular testosterone production and active
spermatogenesis. However, testosterone production occurred in yearling male
otters when paired testes mass exceeded 11 g, with concurrent spermatogenesis
demonstrated. Seminiferous tubule spermatozoa were observed in yearling
testes as early as the first week of December.
No morphological reproductive tract abnormalities were noted during
necropsy, except for a juvenile male lacking apparent external or internal testes.
However, significant inverse relationships were found between hepatic
contaminant concentrations (mainly ortho-substituted polychlorinated biphenyls
[PCBs] and p,p’-dichlorodiphenyldichloroethylene [DDE]) and juvenile male
gonad mass, testes mass, prostate mass and baculum length and mass,
supporting findings from preliminary work. Furthermore, significant inverse
relationships were also found between several OCs and PCBs and adult male
otter baculum length and mass. The inverse relationships found with adult males
implies that the reproductive organ hypoplasia observed in juvenile male otters
continues into adulthood as a permanent effect. |
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