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The impact of nonnative species on river otters and aquatic-terrestrial linkages in Yellowstone National Park . Jamie R. Crait et al. Journal of Experimental Biology 2012. Topic Related to Conservation Biology. Chapter 10- Figure 10.6 Illegally introduced lake trout discovered in 1994.

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Jamie r crait et al journal of experimental biology 2012

The impact of nonnative species on river otters and aquatic-terrestrial linkages in Yellowstone National Park

Jamie R. Craitet al.

Journal of Experimental Biology


Topic related to conservation biology

Topic Related to Conservation Biology

  • Chapter 10- Figure 10.6

  • Illegally introduced lake trout discovered in 1994.

  • Predicted to decrease native cutthroat subspecies

  • Competition for food, lake trout predation, and disease all causing the decrease in cutthroat trout numbers.

  • Decrease will disrupt food web that will affect many threatened species and 42 species in all.

Figure 10 6

Figure 10.6

Figure 10 61

Figure 10.6

  • Much like the example of the opossum shrimp, the invasive lake trout are competing with the native cutthroat trout. Lake trout are devouring native trout’s food sources.

  • Invasive trout inhabits deeper depths of water.

  • Otters in the study heavily depend upon native trout species.



  • Chapter 1 of this dissertation will be discussed.

  • Chapter 1 deals with comparing diving constraints between the high altitude river otter populations and low altitude river otter population.



  • Study aims to describe the biology of river otter populations within Yellowstone National Park

  • This is in the context of a changing food web caused by the nonnative lake trout Salvelinusnamaycush.

  • Several approaches were use to assess the impact of the declining native trout species and the increasing nonnative trout species

Introduction cont

Introduction Cont.

  • Two of the most physiologically challenging conditions encountered by air-breathing animals are the lower partial pressure of oxygen (PO2) at high altitude and O2 deprivation during breath-hold diving.

  • Animals diving at high elevation, however, are faced simultaneously with both of these hypoxic conditions.

Key terms

Key Terms

  • Hemoglobin- the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates. Hemoglobin in the blood carries oxygen from the respiratory organs to the rest of the body where it releases the oxygen to burn nutrients to provide energy to power the functions of the organism.

  • Hemacrit- is the volume percentage (%) of red blood cells in blood

  • Nitric Oxide-A molecule that reacts with the blood vessels to create vasodilation.

  • Serum albumin- a Globular plasma protein essential for maintaining the oncotic pressure needed for proper distribution of body fluids.

  • Blood viscosity- a measure of the resistance of blood to flow. It can be described as the thickness and stickiness of blood.

  • P50- indicates the partial pressure of a gas required to achieve 50% enzyme saturation.

  • Partial pressure (PO2)- is the hypothetical pressure of oxygen if it alone occupied the volume of the mixture at the same temperature.

Chapter 1 high altitude diving in river otters coping with combined hypoxic stresses

Chapter 1:High-altitude diving in river otters: coping with combined hypoxic stresses

  • The study describes the aerobic dive limits (ADL) of the river otters in yellow stone

  • The nonnative trout species habitats are deeper than native trout species.

  • Two otter populations of 5 individuals each were capture and blood samples were taken.

  • Blood-Gas analyses were performed and blood chemistries were compared between populations



  • Sample Population Size: 5 Yellowstone river otters and 6 San Juan Island, Washington river otters

  • Otters were humanely trapped and released after being weighed

  • 20 ml of whole blood was taken from each otter via jugular venipuncture

  • Blood-Gas analysis were performed within an hour of extraction



  • Parametric versus Non-Parametric

    • Parametric- makes more assumptions of structure (more power or misleading)

    • Non-Parametric-makes less assumptions of structure (less power or useful when dealing with non-normal distributions)

    • T-test-it is used to determine if two sets of data are significantly different from each other

    • Mann Whitney U test-is a non-parametric test of the null hypothesis that two populations are the same against an alternative hypothesis, especially that a particular population tends to have larger values than the other.

Statistics in study

Statistics in Study

  • All statistical analyses were conducted with SPSS 18

  • Due to small sample size, some of the data did not meet the assumptions of normality (Kolmogorov–Smironov test and Q-Q plots) and homogeneity of variance.

  • t-tests were used to compare between groups, including hematology (Hct, Hb, and RBCs), concentration of 2,3-BPG, chloride shift, and P50 values.

  • Based on hematological values for the YNP otters it was predicted that levels of NO would be higher in that group than the sea level population, and used a one-tailed Mann-Whitney U-test to test this prediction.

  • The relationships between PO2 and Cl- and HCO3- with regression analyses

P 50 values

P50 Values

Hemotology and blood chemistry values

Hemotology and Blood Chemistry Values

Oxygen dissociation curves

Oxygen Dissociation Curves

Relationship between chloride and lower partial pressure of oxygen

Relationship Between Chloride and Lower Partial Pressure of Oxygen



  • Comparisons of oxygen dissociation curves revealed no significant difference in hemoglobin-oxygen binding affinity between the two populations.

  • The magnitude of the chloride shift and the arterial venous difference in HCO3- were not significantly different between the two populations

  • River otters from the high altitude, YNP population had significantly higher Hct, total Hb, and RBCs than those from the SJI sea level population

  • Yellowstone otters displayed higher levels of the vasodilator nitric oxide, and half the concentration of the serum protein albumin, possibly to compensate for increased blood viscosity.

  • Theoretical aerobic dive limits were similar between high elevation and sea level otters due to the lower availability of oxygen at altitude.



  • Despite diving at over 2000 m in elevation, YNP otters did not display a significant difference in Hb-O2 affinity relative to their sea level counterparts. Instead, to enhance loading of O2, and to protect the tissues from hypoxia during energetically-demanding dives, YNP otters increase Hb concentrations.



  • River otters diving in Yellowstone Lake appear to respond to the chronic hypoxia of altitude primarily via increased Hbconcentrations.

  • The accompanied responses of increased NO, reduced albumin, and relatively large chloride and Bohr shifts indicate that these otters are largely constrained by O tissue demands during high-energy dives favoring increased O storage rather than higher Hb-O2 affinity.

  • These results suggest that recent declines in the native cutthroat trout population could be detrimental to river otters in Yellowstone Lake.

  • Most foraging dives occur in shallow water. YNP otters are unlikely to further modify blood hematology to accommodate the longer and deeper dives required for preying on nonnative lake trout.

  • It appears unlikely that river otters in Yellowstone Lake have the physiological capacity to successfully prey-switch to deep-water lake trout, potentially threatening the persistence of this population.

Literature cited

Literature Cited

  • Crait, J. R., H. D. Prange, N. A. Marshall, H. J. Harlow, C. J. Cotton, and M. Ben-David (2012). High-altitude diving in river otters: coping with combined hypoxic stresses. Journal of Experimental Biology 215: 256-263.

  • Gresswell, Robert E. June 30, 2009. “Yellowstone Cutthroat Trout (Oncorhynchusclarkiibouvieri): A Technical Conservation Assessment” .U.S. Geological Survey.



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