new seal strandings workshop, suzdal, 2012 seal... · 2013. 3. 22. · seal strandings workshop,...

Seal Strandings Workshop, Suzdal, 2012


Potential causes of neonatal separation of pup from mother

disturbance during post-partum bonding (1st hour post-natal)

Vessel or pedestrian disturbance

Disturbance or interference by other seals (not described)

low birth weight

P becomes weak, hypothermic

mother has insufficient milk during 1st days post-partum

Twin birth (Rae, 1969)

Mother has insufficient milk for two pups

accidental birth at sea

inexperienced mother fails to chaperone?

open ductus arteriosis (Courbis, 1997)

poor stamina, weakening, pulmonary congestion

death of mother during labour


A fully documented example is the first recorded

birth in 1989 in the highly industrial Tees estuary, NE

England

Mother caring for pup and nursing it

regularly

Potential causes of low birth weight and postnatal failure to thrive


Stranding of 1989 Tees pup – (i)

Pup appears too weak to follow Mother


Sequence from photos taken over 40 min

period

Mother returns to pup and tries again to get him to follow, but pup is too weak.


The pup later reunited with mother and nursed for 16 min, but stranded

onshore the next day (day 5 post-partum) in an emaciated ( 7 kg)

condition, and died the same day. PM revealed nothing abnormal.

Analysis of blubber revealed ΣPCBs 114 mg/kg, ΣDDTs 9 mg/kg lipid wt.


Ratio of Lone Pups to total Pups during

peak pupping period (Tugidak Isl., Alaska)

0.07 (1978), 0.04 (1994), 0.02 (1995,

1996, 1997, 1998).

0

200

400

600

800

1000

1200

1400

1600

1800

1994 1995 1996 1997 1998

LP

All seals

total P

Jemison & Kelly, 2001 0

50

100

150

200

250

300

350

1994 1995 1996 1997 1998

LP

total P

How many neonatal pups would be expected to strand?


Potential causes of post-natal separation

Storms (Boness et al., 1992)

Human harassment, persistent disturbance

Death of mother


STORMS

On Sable Island 68% of 35 pup separations from mother were due to storms with

peak wind speed >30 kn (Boness et al, 1992). Pups were located by the

observers in the direction of the surface current, an average of 4.9 km from their

origin. Smaller (and presumably younger) females were more likely to lose their

pups.

After storms, females were seen apparently searching for their pups. Three of 16

females that had lost their pups fostered pups which had lost their mothers. Two

Pups died, 7 disappeared and four were successfully reunited with their mothers

by the observers (Boness et al, 1992).


Ballykinler 17/07/10

Colony including mothers and pups before disturbance

Two pups left behind after disturbance


DEATH OF MOTHER DURING LACTATION: PROBABLY UNUSUAL IN

NATURAL CIRCUMSTANCES BUT CORKSCREW INJURIES MAY

BECOME SERIOUS ISSUE

In recent years there have been numerous findings of dead seals – mainly

adult female harbour seals – stranding on shore with ‘corkscrew ‘ Injuries. There were 14

confirmed adult female deaths between July 12 and Aug 03 2010 (Thompson et al, 2010).

These deaths are believed to be due to ducted propellers on vessels requiring accurate

positioning, such as those servicing wind farms. It is thought the propeller sound resembles

the call of a male harbour seal, attractive to a female in oestrus in late lactation.

A female thus killed in late lactation could result in her pup losing its mother at

a suboptimal time and weight for successful and healthy survival of the early stage of

Independence. This could result in increased numbers of underweight pups stranding in

August/September with secondary symptoms of deteriorating health.


OTHER CAUSES OF STRANDING


Table 2. Primary and secondary stranding causes for Pacific

harbor seals along the central California coast from 1992- 2001

Primary causes of stranding Malnutrition 487, Respiratory disease 90, Trauma 76, Otostrongylus

circumlitus related disease 67, Unknown 38, Omphalophlebitis 33

PhHV-1 infection 32, Septicemia 20, Human interference 19

Gastrointestinal disease 14, Neurologic disease 13, Congenital disease 12

Fisheries interaction 10, Protozoal infection 9, Miscellaneous 8

Ocular disease 6, Peritonitis 4, Debris entanglement/ingestion 2

Secondary causes of stranding Human interference 164, Trauma 117, PhHV-1 infection 53

Omphalophlebitis 48, Ocular disease 34, Respiratory disease 20

Oiled fur 19, O. circumlitus related disease 13, Gastric impaction 10

Miscellaneous 8.


Harbour seal lung with large numbers of lungworm (Otostrongylus circumlitus)

causing obstructive bronchitis. http://www.pacificmmc.org/research/downloads/lungwormPaper.pdf

Lungworm is thought to interfere with the respiratory health and diving ability

Of seals and thus alter their ability to feed. All postweaning harbour seals in the North Sea

Are thought to become infected with lungworm from fish once they start to feed,

But this usually only causes illness in seals in poor condition. Seals >1 year old

Develop immunity..


Colgrove et al., 2005


Human interaction as factor in stranding in California (Colgrove et al, 2005).

Most commonly reported from heavily populated areas


http://www.fieldtripearth.org/media_image.xml?object

_id=2676&file_id=6824

Fishing net entanglement is relatively uncommon in harbour seals in California

http://www.fieldtripearth.org/media_image.xml?object_id=2676&file_id=6824




Blood values measured at time of admission of pups were not predictive

of survival during rehabilitation. Mass was associated with survival until

release, and all pups that died weighed less than 10 kg at the time of admission.

66% of 64 pups admitted died, and of the pups which died, the mean number of

days in rehabilitation was 20 (Greig et al., 2010). Causes of death included

septicaemia and umbilical infection (13/22), malnutrition (2/22)

and various other causes.

Greig et al (2010) suggest that haematology should be used to diagnose illness rather

than be used routinely, but initial treatment should focus on minimising risk of umbilical

infection and septicaemia by cleansing umbilical area (and any open wounds)

regularly and using broad spectrum antibiotics.


References Boness, D.J., Bowen, D., Iverson, S.J. & Oftedal, O.T. 1992. Influence of storms and maternal size on mother-pup separations and fostering in the harbor seal, Phoca vitulina. Can. J. Zool. 70: 1640‒1644 . Bowen, W.D., Oftedal, O.T., Boness, D.J. & Iverson, S.J. 1994. The effect of maternal age and other factors on birth mass in the harbour seal. Can. J. Zool. 72: 8‒14 Courbis, S. 1997. Observations of a harbour seal pup (Phoca vitulina richardsii) and human interaction with the pup on a public beach in Lincoln city, Oregon. Hoover-Miller, A., Conlon, S. and Armato, P. 2003. Vessel disturbance of harbor seals in Aialik Bay, Alaska. 15th Biennial Conf. Mar. Mamm. , Dec 14‒19, 2003, Greensboro, N.C. Jemison, L.A. and Kelly, B.P. 2001. Pupping phenology and demography of harbor seals (Phoca vitulina richardsi) on Tugidak Island, Alaska. Mar. Mamm. Sci. 17(3): 585‒600. Muelbert, M.M.C. , Bowen, W.D. & Iverson, S.J. 2003. Weaning mass affects changes in body composition and food intake in harbour seal pups during the first month of independence. Physiol. Biochem. Zool. 76(3): 418‒427.


Colgrove, K.M., Greig, D.J. & Gulland, F.M.D. 2005. Causes of live strandings of northern elephant seals

(Mirounga angustirostris) and Pacific harbor seals (Phoca vitulina) along the central California coast,

1992‒2001. Aquatic Mammals 31(1): 1-10. DOI 10.1578/AM.31.1.2005.1

Greig, D.J., Gulland, M.D., Rios, C.A. & Hall, A.J. 2010. Hematology and serum chemistry in

stranded and wild-caught harbor seals in central California: reference intervals, predictors of survival, and parameters affecting blood variables. J. Wildlife Diseases 46(4): 1172‒1184.

Rae, B.B. 1969. Twin seals in Scotland. J. Zool. Lond. : 243‒245.

Wilson, S.C. 2001. Population growth, reproductive rate and neo-natal morbidity in a re-establishing

harbour seal colony. Mammalia 65(3): 319-334.


Although stranded animals represent an inherently skewed sample of the

free-living population and the prevalence of diseases in live stranded

animals is not the same as in the entire population, assessing temporal

trends in causes of strandings and disease can aid in the evaluation of risk

factors for disease in wild populations. Quantifying the causes of pinniped

strandings also provides information to rehabilitation facilities that can be

used to plan appropriate veterinary care. Tracking human interactions in

stranding events over time can aid in assessing the impact of human

encroachment on the habitat of pinnipeds (Colgrove et al., 2005).

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